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Index: Samurai Jack | Scotsman & Family | Other Allies | Aku | Cult of Aku | Ashi | Other Enemies | Comics

Aku note
"You might have beaten me now, but I will destroy you in the future."
Voiced by: Mako (Seasons 1-4, Shadow of Aku, Season 5 Episode 10 (archived audio)), Greg Baldwin (Season 5, FusionFall, Battle Through Time), Fred Tatasciore (Cartoon Network: Punch Time Explosion)

"Who Dares? to summon the Master of Masters, the Deliverer of Darkness, the Shogun of Sorrow, Aku?"

Long ago—very long ago—a single small fragment of an Eldritch Abomination fell to Earth, wiping out the large saurian creatures that dominated the planet at that time. It existed as a mindless evil for millions of years until a brave king attempted to destroy it: the attempt to destroy it instead gave it consciousness. It became Aku, a being of pure darkness and evil. When a noble samurai came to fight him, Aku tore open a portal in time and flung him into the future, where he is de facto ruler of the world. Now, the samurai called Jack has drawn every drop of his ire, and he devotes a lot of effort to finishing him once and for all.

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  • 0% Approval Rating: In a notable subversion, "Aku's Fairy Tales" shows Aku as aware of how his subjects view him, which leads to a clumsy attempt to persuade children to like him. Outside of that instance, Aku seems not to care (since nothing his subjects could do can hurt him). The only reason his approval rating hits zero percent, however, was Jack — he showed people that a world without Aku could possibly exist. Anyone who ever follows him only does so to feed their own personal ambitions. In the Grand Finale, when he captures Jack and announces his plan to publicly execute him, everyone Jack has ever helped storms Aku's fortress en masse to save him.
  • Abandoned Catchphrase: Downplayed. In Season 5, Aku still calls Jack a "fool," but it's only once or twice.
  • Abusive Dad: Once he finds Ashi with Jack and realizes she was conceived from his essence, he forcibly bends her to his will using the extract of himself that's still within her, turns her into a demonic version of herself, and forces her to fight and betray Jack. To his credit, at least he was honest about it and he was a little more encouraging than her mother. Later, he also tried to kill her.
  • Achievements in Ignorance: Some of Aku's closest victories against Jack happened completely without his knowledge.
    • Aku once accidentally infected Jack with a flu he was carrying, and then withdrew to his fortress. Unbeknownst to him, this virus began to slowly transform Jack into a smaller version of Aku, taking over his personality and driving him to the brink of madness and villainy.
    • After Aku destroyed the final time portal by blowing it up with his eye beams, he mocked Jack for his failure to escape the future and tricked him into killing some cute, innocent animals. This event would up kicking off Jack's Despair Event Horizon, beginning with the loss of his sword. Aku viewed this idea as a failure since Jack couldn't die of old age, but killing off his last hope of returning home in such a painful and spiteful way almost caused Jack to commit suicide.
    • Happens yet again. It turns out that the Daughters of Aku are literally his offspring. Years ago, he paid a visit to his cult and filled a goblet with his substance to humor them. He didn't expect the High Priestess to actually drink it. The result is that Aku indirectly fathered seven exceptionally deadly children who came closer than anyone else to actually killing Jack. It ultimately leads to Aku turning his last living daughter, Ashi, into a powerful puppet that forces Jack to surrender because of his feelings for her.
  • Achilles' Heel: Aku is very weak to divine magic, as his Made of Evil physiology can be burnt apart easily by the magic. The formless evil that spawned him was slain by a trio of gods who later imbued Jack's sword with the same energies, allowing it to harm Aku. Aku can No-Sell just about anything else, unless it's of divine origin; and even episodes like "Jack and the Gangsters" shows Aku being defeated by the Water Goddess and her minions. It's also shown that even magic such as that from the Scotsman's Celtic runes can ward him off, as can the Robo-Samurai, which is explicitly an ancient magical giant.
  • Action Dad: Aku regularly (and effortlessly) decimates entire armies, has conquered the entire universe, and is one of the few beings that can fight on par with Samurai Jack. And he also happens to be a father (albeit a deadbeat one, which he wasn't even aware of until recently).
  • The Ageless: Immortal. That's pretty straightforward.
  • Anarcho-Tyranny: Instead of a totalitarian regime where everything is strictly monitored and controlled, Aku allows the whole world to be consumed by an endless state of violence and warfare in which all sorts of villains, warlords, criminals, and monsters run rampant and terrorize innocent people as they please. Aku himself is so far beyond anybody else on the planet in terms of raw power that he could be an unstoppable domineering tyrant if he wanted to, but he really only intervenes personally if such cruelty were amusing to him (or to fight Jack, his archnemesis—and the only person capable of harming him).
  • And There Was Much Rejoicing: Even Ashi - his own daughter - was glad that Aku kicked the bucket. Jack's friends and mentors from all over the world likewise come to Japan to celebrate Aku's demise.
  • Antagonist Abilities: As the Big Bad, his powers are designed to give him an edge that everyone else lacks. He is virtually indestructible, can shape-shift into several monstrous forms or into anyone else to deceive people, observe others from a distance among other things. There are very few beings on the side of good that are capable of matching him in raw power.
  • Antagonist in Mourning: Inverted. In Season 5, Aku has fallen into a deep depression, because after 50 years, Jack has not died.
  • Arch-Enemy: At first he was one to Jack's father, now he's one to Jack himself. In Jack's case, however, it's deconstructed. After sending Jack to the future in a last-ditch effort to save himself, Aku has spent most of the series trying various schemes to destroy him to no avail and realized that it was quickly turning into a draw between the two. To that end, Aku decided to simply destroy all the time portals and let old age do the rest. However, an unforeseen side effect of the time magic caused Jack's aging process to stop, making him biologically immortal — meaning that Aku has essentially trapped himself in an eternal stalemate with Jack, much to his dismay. Too bad he didn't know Jack lost his sword shortly after, as Aku not only spent decades in a completely avoidable depression when he could have killed the unarmed Jack easily, he didn't find out about Jack losing the sword until after Jack got it back.
  • Archnemesis Dad: Ashi is very willing to disown him as her father by helping Jack kill him.
  • Asshole Victim: Exaggerated; while he is far from being your certain average asshole, he still reacts horrorfully whenever he pretends to be defeated.
  • Attack of the 50-Foot Whatever: His default form is usually several stories high. And he is only a fragment of what he came from.
  • Authority Equals Asskicking: Aku is the supreme emperor of Earth and many other worlds, and it's not hard to guess how much of a badass he had to be to get there. In fact, come the Season 3 Episode "Jack and the Zombies" and, without the sword to give him an advantage, Jack is pretty much put on the ropes by Aku as the latter matches him blow-for-blow in swordplay and outmaneuvers him with his shapeshifting - heck, if wasn't for Aku not knowing Jack couldn't be hurt with his own swordnote , Aku would have killed Jack then and there.
  • Ax-Crazy: A sadistic demon who commits carnage and torture for his own sick entertainment. In "Jack and the Zombies", he's very much the living embodiment of this trope. Notice his maniacal cackling while fighting Jack. During the beginning of the fight, Aku's laugh is absolutely psychotic, and then he goes on a murderous rampage.
    Aku: "Oh Samurai? Where are you Sa-mu-rai? You can run but you cannot hide, CAUSE I CAN SMELL YOUR BLOOD!"
  • Badass Baritone: Greg Baldwin gives him a lower voice pitch than Makoto Iwamatsu, which makes it all the more appropriate for the Shape-Shifting Master of Darkness.
  • Badass Boast: Who dares to summon the Master of Masters, the Deliverer of Darkness, the Shogun of Sorrow, Aku?
  • Bad Boss: Aku plays with this trope. One good example being with Scaramouche in season 5. Aku treated him like a friend rather then an employee, but once Scaramouche made a mistake, Aku blew Scaramouche up before he could say a single word, never giving him a second thought.
  • The Bad Guy Wins: The whole premise of the show involves Jack having to go back to the past to undo Aku's victory and conquest of the galaxy, which happened because Jack was not given the opportunity to land the killing blow thanks to being forced into Aku's Bad Future.
  • Bad People Abuse Animals: Not even animals are safe in Aku's tyranny, especially dogs.
  • Beard of Evil: That's a pretty stylish goatee of flame.
  • Beware the Silly Ones: Aku is a lovable goofball... and utterly evil.
  • Big Bad: His goal of spreading his evil throughout the world as well as as casting Jack into the Aku-ruled future is the impetus of the entire plot. Jack can never fully win until he finally gets back to the past and destroys Aku. His whole goal is to kill Jack so he can't complete his quest. By Season 5 however, Aku has less overall appearances and no longer has any plots that involve antagonizing Jack, because after thinking Jack would die of old age, but didn't due to being The Ageless he's pretty much out of ideas.
  • Big Bad Ensemble: With the High Priestess and Jack's Inner Self later revealed to be Mad Jack in Season 5.
  • Big Brother Is Watching: He possesses a screen that allows him to constantly watch Jack wherever he is. It was only interrupted when Jack entered a particularly holy place — resulting in old-fashioned TV static. By the time of Season 5, however, he's long since given up on using it... meaning he doesn't know that Jack's lost his sword.
  • Big Ol' Eyebrows: Made of literal flames.
  • Bond Villain Stupidity: Throughout the series, Aku shows that he's enough of a sadist that he personally prefers to torment his enemies before (or instead of) killing them.
    • Once, he disguised himself as a beautiful woman to trick Jack into leading him to a magical jewel with time travel capabilities. During that time, he forgoes multiple opportunities to kill Jack, whose guard was lowered down significantly.
    • This becomes his undoing in the series finale. After placing Ashi under his thrall and forcing Jack to surrender himself and the sword, Aku, rather than just killing Jack on the spot, decides to take him back to his lair so that he could broadcast Jack's Public Execution before the entire world, which ends up prompting the Scotsman and Jack's other allies to mount a rescue attempt. Then, Aku ends up wasting time trying to think of inventive ways to kill his foe before finally settling on having Ashi play the role of Jack's executioner, right before the Scotsman's army attacks Aku's tower, allowing Jack to regain the sword, Ashi to break free from her father's control, and both of them heading back into the past to destroy Aku for good.
  • Boring, but Practical: Despite his vast empire and armies of robots and bounty hunters, Aku has no issue with Boring, but Practical tactics.
    • While Aku does possess actual skill in his powers and shapeshifting, averting the Unskilled, but Strong trope, Aku generally just breezes by any direct confrontation without putting any real effort into things. Since he's almost impossible to actually hurt, there's no reason for him to do more than the bare minimum in combat unless he's fighting Jack.
    • The beetle drones that Aku uses to subjugate the populace are helpless against stronger resistances to his reign, like Jack or the Scotsman, but given they can handle the majority of the world's populace with ease, there's really no reason to stop using them.
    • Between seasons 4 and 5, Aku decided to stop trying to kill Jack directly and let time take care of his rival by just waiting for him to die of old age. This would have gotten rid of Jack with no effort for Aku, and only failed because of something neither party could foresee.
    • In XCVI he assumes the form of a giant black ball, easily the most mundane of all the forms he has assumed throughout the series. However, when using it against the army attacking his tower, it also turns out to be viciously effective, with him literally steamrolling hundreds, if not thousands, of soldiers in a matter of seconds.
    • In the series finale "Episode CI", after getting beaten up by the Robo-Samurai, Aku hits his breaking point and transforms into a giant dark cloud and begins raining down spikes on all of Jack's allies during their rescue attempt. It's one of the most mundane and simplest forms he's used, but it's deadly effective as he kills nearly everyone save for the 300 warriors (who blocked with their shields) and the Scotsman's daughters, who are protected by the Scotsman's bagpipes.
    • Also in Episode CI, Aku can't decide which elaborately formed blade he wants to use to publicly execute Jack and asks Ashi to do it for him, and ends up lampshading this trope when she forms a simple lance.
    Aku: "The simplest solution is the usually best one."
  • Breakout Villain: By far one of the most iconic Cartoon Network villains. Aku has practically become synonymous with the series and was listed in videogames such as FusionFall and Cartoon Network: Punch Time Explosion.
  • Break the Badass: Jack has managed to do this to him come Season 5. 50 years of trying and failing to kill Jack, exhausting every possible method to do so including simply destroying the time portals and letting time do the job have failed. Aku is left a Nervous Wreck too scared to leave his own lair and near the Despair Event Horizon. It takes finding Ashi to finally snap him out of it.
  • Breath Weapon: Can breathe fire in both his normal form and whenever he turns into a dragon.
  • But for Me, It Was Tuesday: Best shown in "Jack vs. Aku." While Jack considers it his life's mission to kill Aku and treats their ongoing battle with the utmost seriousness, Aku considers their conflict to be some kind of game, one that's gotten a bit long and tedious. Subverted come Season 5, as 50 years of failure has decidedly taken its toll on Aku and more or less broke him.
    • Aku is ultimately surprised at the existence of Ashi because he was doing little more than jokingly humoring the Cult of Aku with a gift, when he paid them a visit. He really has to think back to remember doing it, too. Before that, he didn't even recognize the Scotsman as being one of his main enemies, even when he clearly had the means to harm him. All this chalks up to Aku having a rather poor memory.
  • The Caligula: Not only commits carnage and genocide on a regular basis, he is more than willing to welcomes a lot of criminals and gangsters in his Bad Future, a surprisingly disturbing dystopia.
  • Card-Carrying Villain: Often refers to himself by several evil-sounding titles such as "Shapeshifting Master of Darkness", just in case you couldn't tell he was evil by looking at him. He also openly mentions his "unspeakable evil" in the opening of the show's first four seasons. Oddly, he did have one attempt at being a Villain with Good Publicity instead. It... didn't quite go as planned.
  • Catchphrase: He often refers to Jack as a "Foolish Samurai!"
  • Characterization Marches On: In the pilot episodes, he's actually quite a fairly serious, ominous antagonist, lacking a lot of the dark sense of humor that would characterize him later on. Aku was also much quieter, though still dramatic. In the episodes showing how he was born, his personality is as serious as in the pilot episodes, which indicates that the timeskip changed him greatly.
  • Chekhov's Skill:
    • Aku's ability to smell a person's blood, first referenced in his very first encounter with Jack where he recognizes him as the son of the Emperor who first defeated him and referenced again in "Jack vs the Zombies" where he managed to find Jack when he was hiding. It's one of his least used abilities, but it's also the most useful as shown in the penultimate "Episode C" where he correctly deduces that Ashi is his biological daughter.
    • His ability to infect living things with his evil and turn them into an Aku clone. This ability was first seen in "The Aku Infection" when Aku accidentally sneezes on Jack while suffering a cold, making it seem that he didn't even know he had this ability. Season 5 gives this power more focus where in "XCVIII", Aku uses his magic to transform the three rams that were helping Jack into monsters for the samurai to vent his anger upon after Aku destroys the last time portal. In "C", upon discovering Ashi is his biological daughter, he infuses her with his power and turns her into a puppet under his control. And in the final "Episode CI", he uses this to corrupt some of Jack's allies when they come to rescue him.
  • Child Hater: As shown in "Aku's Fairy Tales", Aku really hates children, because all they do is mock him.
  • Chronic Backstabbing Disorder: See Stupid Evil. He nearly always betrays anybody he works with, even when he has nothing to gain from it.
  • Cold Ham: Was this in the beginning of Season One before graduating to a full-fledged Large Ham.
  • Combat Pragmatist: In contrast to Jack's consistent Honor Before Reason (well, before the time skip, at least), Aku won't even go up against Jack at all unless he's got an edge that will let him win, and consistently tries new plans to potentially murder him over the course of the series. These range from getting Jack to agree not to use his sword, turning the sword against him, and outsourcing the job to any assassin he can find. Season 5 reveals that Aku has long since exhausted all possible routes to kill Jack (and destroyed all of the time portals) so he's fallen back on playing the long game; withdraw all contact from Jack and just wait for the Samurai to die of old age... then falling into a deep depression when Jack turned out to be The Ageless. He will only come out if news of Jack's death is confirmed or if, as Scaramouche reveals, Jack becomes vulnerable (i.e., losing his sword).
  • Combat Tentacles: Whenever he's in octopus form (one of his favorites) or reverts to formlessness.
  • The Comically Serious: He's always funnier when he's trying to be serious. As Genndy Tartakovsky stated, he's meant to have a serious personality but humorous at the same time.
  • Complete Immortality: He hasn't aged at all since the day he was 'born' and heals from injuries almost instantly. The only weapon that causes him real harm and can kill him is Jack's sword, and by extension presumably the three gods (Rama, Odin, and Ra) that forged it and destroyed the original primordial Black Mass he was spawned from. He can be held at bay by a few other entities (notably the water goddess from the backstory of "Jack and the Gangsters", the Ancient Master from "Jack and the Monks" and later on the Scotsman's Spirit with his Celtic Magic), but not really injured due to lacking the necessary raw power or methods.
  • Con Man: Aku is certainly a master of this. He has no qualms about promising whoever makes a deal with him big promises and then betraying those promises.
  • Creepy Monotone: In earlier episodes, most notably the Pilot, Aku spoke with a very emotionless, low tone and hardly ever raised his voice. As time went on though, we saw his less serious side come out more often than not.
  • Cruel Mercy: If Aku decides to spare someone's life instead of taking it away, it's only because he's got something much worse in store prepared for them. For example, he could've easily killed the Emperor after he was born, but Aku found forcing him to watch while he massacred the Emperor's people much more satisfying.
  • Curb-Stomp Cushion: Most fights between him and Jack consist largely of Aku getting slashed to pieces by Jack's sword, though he'll usually put up some showy tricks for Jack to evade and maybe land a good hit or two to remind the audience barely any other entity can oppose him. And should Jack ever temporarily lose grasp of the sword, he's instantly left on the defence until he gets it back.
  • Dark Is Evil: In addition to being mostly black, his primal form is nothing but a billowing dark mass.
  • A Day in the Limelight: "Aku's Fairy Tales", which focuses on his attempts to win over a group of children. Jack only appears in his stories. Also, the "Birth of Evil" two-parter focuses mostly on his origin and his rivalry with Jack's father.
  • Deadpan Snarker: Depending on his mood, Aku can throw out some dry and venomous one-liners at times.
    Jack: "AKU!"
    Aku: "Yes, it is I, Samurai Jack. How incredibly observant you are."

    Scientist: "Master. Master. We've done it. May I introduce: THE MOST EPIC VERSION OF THE BEETLE DRONE YET!" (Evil Laugh)
    Aku: "And I care because...?"
  • Deconstructed Character Archetype: On what it means to be Made of Evil and a Card-Carrying Villain. As part of a malevolent monster that just wanted to destroy the universe, Aku has relatively simple desires, and is very well-known as a back-stabber. This has shown to actually hurt his chances at killing Jack in the long run, as he simply CAN'T stop being evil because it's in his very nature to be evil. This is partly the reason why his attempt to win over children with fairy tales failed; because the children are well aware of his reputation as an evil tyrant and know full well that someone like him can never be a hero. One time he actually did try living up to his end of the bargain, and even then he subconsciously back-stabbed the one he was dealing with. Thus showing the folly of being only evil; you can only pay evil unto to others even if it screws yourself over, too.
  • Deader Than Dead: Future Aku, after Jack travels back and kills his past self, erasing him from history.
  • Defeat Equals Explosion: Aku, and his lair, goes out with a bang once Jack finally does him in.
  • The Devil Is a Loser: Played with. There's no denying that Aku is an incredibly powerful force of evil. But when it comes to Jack he falters. His Bond Villain Stupidity and Chronic Backstabbing Disorder often results in Aku foiling his own plans at the last moment. Aku's treacherous nature is so predictable that even Jack prepares for it - to the point where he can outwit Aku. Also, Aku's confrontations with Jack usually end with Aku forced into a humiliating form, just to escape. At the end of Season 1, Aku tells stories to children about how he's amazing and how horrible Jack is. None of the children are convinced and Aku's stories devolve into nonsense. By Season 5 Aku has fallen into a deep depression and is seeing a therapist. Said therapist is himself, who ultimately can't help Aku at all.
  • Despair Event Horizon: He seems to be toeing the line as of Season 5. Sick of constantly failing to kill Jack, he withdrew to his lair in an attempt to just let time take its toll on Jack, as he had destroyed every way for Jack to return home. It would've been a good idea... if Jack had not become The Ageless. Now Aku has been reduced to moping around his lair, not really caring when his scientists show him a new model of the beetle drones, and having therapy sessions with himself.
  • Determinator: Considering the many times that Aku has failed at defeating Jack, Aku will stop at nothing to get him destroyed. Finally subverted as of Season 5. After every single strategy he's come up with to kill Jack has failed (up to and including just waiting for him to die of old age), Aku's officially run out of ideas. He's since fallen into depression and apathy over Jack's continued survival.
  • Diabolical Mastermind: Very cunning and deceiving - when he wants to be, at least.
  • Didn't See That Coming:
    • Aku genuinely had no idea displacing Jack in time would make him The Ageless. As a result, his attempt to just destroy any way for him to get home and then let time kill Jack for him failed, and Aku is beside himself (in one scene literally) because that was really his last resort.
    • Gave the High Priestess some of his essence to worship after being flattered by their devotion to him. He didn't expect her to actually drink it. Works out in the end for him though... until Ashi breaks free.
    • He never expected The Power of Love could break Ashi free from his control with all his powers. This includes time travel, allowing her to send Jack back in time to kill past Aku.
    • It's safe to say Past Aku didn't expect Jack to find a way to return and appear only a few moments later, 50 years stronger and more experienced while Aku is still battered from their previous fight.
  • Dirty Coward: Since Jack's sword is the only weapon that can truly hurt him, Aku largely avoids direct confrontation with him, only doing so when he has some kind of advantage. And when he loses that advantage, you can guarantee that he'll pull a Villain: Exit, Stage Left. While some might call this prudent, the way he reacts to setbacks in fights against Jack makes it pretty clear that this caution is emotion-driven rather than strategically-based, which is also somewhat more fitting with his general characterization. Jack even calls him a "cowardly shadow" on one occasion. Come Season 5, he's so scared of Jack he's basically hunkered down in his lair, hoping someone will take care of Jack for him. The Scotsman calls him on it to his face, which Aku doesn't take very well. And at the end, Aku dies a coward when Jack finally returns to the past just seconds after Aku had sent his younger self to the future, pathetically trying to flee from his very furious nemesis rather than try to fight back.
  • Disappeared Dad: He was absent throughout the entire life of his daughters, and didn't even seem to be aware of their existence until he found Ashi.
  • The Don: He runs an extensive criminal empire dedicated to contract killing and slavery, has extended his reach to other the galaxies to increase his wealth and power over resources and the masses, and employs a lot of mobsters, enforcers, Elite Mooks, thugs, minions, bounty hunters, assassins, dictators and interplanetary gangsters at his disponsal.
  • Do Not Adjust Your Set: He pulls this off in the Grand Finale, broadcasting his capture of Jack to the entire world and declaring his intent to publicly execute him in order to permanently crush everyone's hopes and set an example for anyone who would oppose him.
  • Do Not Go Gentle: His usual response to a serious setback is to run away. But if that's not an option, he'll fight ferociously with every resource he's got. Subverted with his actual death, where he is still extremely weak from the beating Past Jack gave him right before the even stronger future one comes back. The last few moments of Past Aku's life than consist of desperately trying to escape from Jack in complete panic.
  • The Dreaded: He's called Aku for a reason. He is a demon so feared that his return after Jack's father first defeated him would spell doom for the world. People know better than to cross him and elders often warn children to think twice before speaking ill of him. His followers often fear getting on his bad side when in his presence, as shown in "Jack and The Gangsters" when the titular gangsters report back to him and they think anyone who tries to fight him is out of their minds. Plus, when Aku appears before an audience of children in "Aku's Fairy Tales", they are absolutely terrified.
  • Dreaming of Things to Come: His ability to have prophetic dreams allowed him to undermine one of Jack's missions since he saw it before it happened.
  • Dystopia Justifies the Means: He rules all of Earth and beyond with an iron first, but he has to make life under his regime as horrible as possible by giving any manner of evil free reign. With the occasional Hope Spot for those poor mortal fools, otherwise it's no fun.
  • Eldritch Abomination: A bit watered down compared to the the run-of-the-mill versions. While his origin is completely Lovecraftian his demenor is less so. Like many Lovecraftian entities, he can take various forms according to his intentions but Aku himself is actually very human in his motivations and thinking. In spite of being an abomination that's Made of Evil, Aku's only desires are to cause pain and suffereing and rule the universe like a king. He's basically demonic version of Ming the Merciless.
    • Played Straight with the black shadow he came from that was trying to eat the universe and could even eat gods if given the chance. The black mass Aku came from had no definite form, constantly shifted its shape amorphously, and was incomprehensible from an intelligence and morality standpoint.
  • The Emperor: Once Aku took over the world, he turned it into an extremely corrupt empire where he governs.
  • Evil Cannot Comprehend Good: His Fatal Flaw. Given that Aku is the Anthropomorphic Personification of evil, it's only natural that he suffers from this trope. Many of Aku's schemes fail because he has no understanding of the concept of good.
    • This trope is why him sending Jack to the future backfired. He'd expected a world ruled by him would allow him to crush Jack effortlessly when he arrived. He never took into account that a hero arriving and successfully resisting him would trigger Hope Springs Eternal and start giving the oppressed masses someone to rally behind.
    • Additionally, other things that are lost on him are "respect" and "teamwork", as he has Chronic Backstabbing Disorder to the highest degree and has actually screwed himself over time and again because he cannot help but betray his allies in some form or another, even when he's trying really hard not to.
    • Also shows in the episode "Aku's Fairy Tales" when, out of a desire to be admired, he tries to make himself out as the good guy in the stories he tells to children... and one of the prime reasons it doesn't work is that he can't really comprehend what "good" means — the closest he can come to understanding heroism is "free beef jerky for all"!
    • In the episode "Jack and the Hunters", Aku hires the Imakandi to hunt down and capture Jack, promising them a handsome reward if they're successful. However, what he failed to take into account (and what they outright tell him), is that they hunt not for wealth, but for the thrill of the hunt. So when he finally captures Jack, he's given them such a challenge that they choose to set Jack free out of respect rather than deliver him to Aku. Aku does not take it well when they break off their deal.
    • In the finale, his execution of Jack fails because he couldn't comprehend that rather than being crushed by this, the ones Jack inspired would come to his aid en masse. Later on in the same episode, he finally meets his end because he never believed his daughter Ashi could free herself from his control, letting her use his powers he awakened in her to take Jack back to the past and kill him.
  • Evil Genius: Zig-zagged: Aku always has a strategy for his evil plans, but he fails pretty regularly. He has, though, planned some very intelligent and cunning schemes, such as transforming into a woman who saves Jack's life to trick him into finding the portal he's trying to reach, only to destroy it. He clearly isn't a dimwit - he did subjugate the Earth - but he's prone to errors in judgement.
  • Evil Gloating: What's the point of hurting people if you don't get to revel in their expressions of horror, despair and hatred? Well, maybe avoiding when that doesn't take and they instead rise up against you to save your mortal enemy, as happened in the series finale.
  • Evil Is Angular: Where to even start? Rectangular Horns of Villainy? Check; Fangs Are Evil? Check; Rectangular head? Check! Triangular upper torso in his Shapeshifter Default Form? Check; Shoulders that look like a skeleton is stretching the skin to give them axehead-edges? Check! Creepy Long Fingers ending in a talon-like claw? Check! Has a home in Mordor where the his mere presence have corrupted the land and given the trees a leafless, irregular spiked look? Check-mate! Really, even if this guy wasn't pitch black, you'd instantly peg him as the villain.
  • Evil Is Bigger: Much bigger, but mostly because he prefers to be big as his standard form.
  • Evil Is Hammy: The way he talks is so bombastic and over the top!
  • Evil Is Petty: Despite having higher goals and ambitions, Aku cannot resist committing unnecessarily cruel and petty acts to people he's already screwed over, often to prove he can or just for a sick kick at their expense. He ends up taking it to Stupid Evil levels as he always backstabs anyone he makes a deal with, just to laugh at their misfortune.
  • Evil Laugh: Sincere, sinister, and usually preceded by something terrible happening to someone.
  • Evil Old Folks: Aku is hundreds or even thousands of years old, and is a being powerful enough to conquer the galaxy.
  • Evil Overlord: Aku is what Sauron would have been if he had conquered Middle-Earth and extended his control beyond the stars. An inhuman being of darkness with control over the entire worlds and unlimited resources at his disposal: from gangsters, mercenaries and criminal networks to entire hordes of robots, aliens and demons to throw at our hero. He's also a Sorcerous Overlord, Galactic Conqueror, and God-Emperor all rolled up into one.
  • Evil Plan: Conquering the Earth was a done deal before the pilot ended. The one that drives the plot is his attempts to kill Jack, and, failing that, prevent him from traveling back in time.
  • Evil Sorcerer: Aku primarily relies on his magical powers for fighting enemies and terrorizing people.
  • Eviler Than Thou: Manages to pull one on the High Priestess. While she tortured her daughters growing up, her daughters did follow her out of genuine belief in her and had free will of their own, warped though it may have been, and the Priestess did in fact think her actions were for a greater cause than herself. Contrasting this, Aku forces Ashi to attack Jack outright by puppeteering her body - in which he not only gives his own daughter no say in the manner, but he doesn't even try to convince her that Jack's the bad guy and he's the hero the way the High Priestess attempted to; he knows he's the bad guy here, he's loving every damn minute of it and he especially loves making sure they know it. Of course, being the very incarnation of evil itself, Aku is the biggest fish in the pond of villainy, so this trope is more or less a given, but it can be very easy to forget given his more hammy tendencies.
  • Evil Sounds Deep: As Mako once said, "Evil comes from the belly."
  • Evil Sounds Raspy: He has a raspy voice which matches his Evil Laugh.
  • Eye Beams: Multiple types for multiple purposes; force blasts, incendiary force blasts, alchemy, summoning, teleportation, transformation, necromancy, and general spellcasting. Basically, whenever Aku's feeling lazy, he'll just use his eyes.
  • Famous Last Words:
    Future Aku: "Oh no." (Episode CI)/"This is not over!" (Battle Through Time)
    Past Aku: "No, wait!"
  • Failed a Spot Check: Aku mentions in passing that the only thing that has changed about Jack in the last 50 years is "he just grew that stupid beard." Jack only grew his beard after he lost his sword, a detail that Aku is completely unaware of for years. However it is unknown if Aku actually saw Jack with his beard himself or if one of his minions simply informed him of this and also missed the fact that Jack has no sword.
  • Fangs Are Evil: His have the distinct Oriental pattern in which the canines curve outward.
  • Faux Affably Evil: Sometimes friendly, sometimes vicious, and sometimes vicious with shades of friendliness. Aku is funny, cheerful and affable on the surface and is certainly capable of having nice, civil conversations with people, but he's also an Ax-Crazy maniac who loves to bring misery and suffering to everyone in reach. He would probably be one of the darkest Cartoon Network villains if he wasn't so damn hilarious to watch.
  • Final Boss: He's the final antagonist Jack encounters during his long journey.
  • Final-Exam Boss: In "Jack and the Zombies".
  • Flaming Hair: He has flaming eyebrows and a matching beard.
  • Foil: He's very much the exact opposite of Jack. While Jack seeks to do good wherever possible, even at risk to his well being and goal of returning to the past, Aku always seeks out any action where he makes life miserable for others — even if it would be to his disadvantage in the long run. Their colors and designs likewise contrast as well - Jack is a humble prince in all-white robes who is selfless, empathetic, dutiful and the epitome of an honorable man, while Aku is an all-black demon-sorcerer who is selfish, callous, treats the world as his toybox and the epitome of pure evil. Likewise, they also have opposing meaning in their titles — Jack's is "Samurai", which is generally associated with a humble and honorable warrior, while one of Aku's titles has him call himself a "Shogun", which is more in line with a ruler and supreme commander of an army.
    • Season 5 in particular highlights their different reactions to their stalemate: while Jack forces himself to keep moving and fighting for mankind, Aku completely gives up on beating Jack and retreats from the public. Notably, Jack's hallucinations damn Jack for his inaction, while Aku begins talking to himself to try and feel better about his failure.
    • He's also a foil to the Black Mass that he came from. The shadow was huge (galactic in size), had a constant changing shape but no true form, never spoke or even exhbited intelligent behaior while acting as little more than a beast with whatever motives it may have had being completely inscrutable. Lastly, it didn't want to rule the universe, it wanted to EAT THE UNIVERSE and everything in it.
  • For the Evulz: The only real explanation for most, if not all of his actions: Aku does what he does because the suffering of others amuses him, as demonstrated by his signature psychotic laugh. Justified, as he is literally Made of Evil, and Deconstructed, since a good half of his plans are foiled by his own inability to be pragmatic.
    • Far more profound, however, is the evil that Aku has unleashed upon all the inhabitants of Earth. To have a brutal industrialized hellscape is one thing, but to populate it with criminals and overlords who assist Aku in creating "a world where the innocent and the weak are always preyed upon," in Jack's description, is entirely different. The true evil of Aku is that he has dehumanized the world, reduced the inhabitants of Earth to a Darwinian struggle in which strength and cunning untethered from morality prosper. It is a world not merely of "catastrophe, devastation, and carnage," as Jack says, though it is certainly that. More devastating, though, is that it is a world where vices have become virtues, where children have become slaves to evil and manipulation (of particular import to Ashi, raised as a brainwashed child soldier), where restraint and mercy lead only to death and ruin, where the few pockets of innocence and joy are singled out for ruination, where underlings do not merely carry out evil orders but torture for pleasure (calling it "fun"). This is the unspeakable evil Aku has unleashed. All for his own enjoyment.
  • Four-Fingered Hands: Considering he's thoroughly evil, there's probably a meaning to it. As of Season 5, he's now got the full set. Given that he's a shapeshifter, he can grow extra digits if he wanted.
  • From a Single Cell: If Aku is cut down, but left alone, he will regenerate from whatever is left of him. This is exactly the nature of the original Dark Mass—a huge fragment of it landed on earth, and it regenerated as Aku with the help of magic arrows. This is why Aku has to be thoroughly destroyed. Jack finally kills him by completely destroying him with the sword.

  • Galactic Conqueror: Ruling the Earth wasn't enough, so he extended his dominion to other planets. It's not clear whether he's conquering them or just laying waste to them, but he's garnered enough attention to attract aliens (usually traitors, criminals, and bounty hunters) of all sorts to the Earth.
  • Gave Up Too Soon: After Aku destroys the last time portal in existence and taunts Jack over it he immediately retreats, knowing Jack can still kill him with his sword, to try to wait for Jack to die of old age and stops only to turn three cute mountain lambs into monsters to attack Jack. Had he stayed to watch the fight, or paid closer attention to Jack afterwards he would have discovered that Jack lost his sword after this event and was vulnerable for years. Instead he hides in his lair for decades, depressed that he and Jack have reached a stalemate due to Jack's immortality and inability to return to the past.
  • Gender Bender: He has turned himself into a woman to fool Jack more than once.
  • Genius Bruiser: He's a powerful demon. That, and his surprisingly smart knowledge of human nature, being able to manipulate the feelings of others for his own convenience.
  • Genius Ditz: While Aku can be smart and cunning, his plans are not always the most well-thought ones.
  • God-Emperor: He's the absolute ruler of the Earth and has all the power to go with it.
  • God of Evil: He's an immortal and malevolent cosmic entity who is worshiped by an evil cult.
  • Go Mad from the Isolation: Season 5 shows that Aku has become depressed and unenthusiastic towards his subjects and scientists. After having destroyed all the time portals on Earth, he retreated into his lair to wait out Jack until he dies of old age, but after 50 years Jack hasn't aged at all and Aku hasn't made contact with him since out of fear.
  • Greater-Scope Villain: Became one in Season 5. Sure, he's still the chief antagonist, but a lot of antagonists have more involvement than himself in the plot such as Scaramouche (Aku's favorite assassin), the High Priestess (the woman who raised the Daughters of Aku), the Dominator (a brutish, tyrannical man in Aku's employ) and Lazarus-92. On the other hand we have the Omen and Jack's Inner Self later revealed to be his Evil Counterpart, who serve as a more psychological threat to Jack. So yeah, Aku never directly acts against Jack (at least until "C"); instead, it's the other mentioned characters that cause trouble for Jack.
  • Green and Mean: He has a green face and many of his disguises are associated with the color. As for mean... well, just see the rest of this page.
  • Grumpy Old Man: By Season 5, his attitude is akin to that of an old geezer too crabby to even talk to anyone, and constantly complains about the racket neighbors are making. Especially when Aku complains of all the noise happening outside his tower, which is really being caused by an enemy army's attacks.
  • Guttural Growler: Shines through quite a bit in Season 5 with his new voice actor, replacing the dearly departed Mako.
  • Hair-Trigger Temper: Aku has an explosive temper towards anything. In fact, questioning his authority and messing with his ego are probably the most dangerous things you can do. Furthermore, he kills people for the slightest offenses towards him.
  • Healing Factor: Aku can quickly recover from any damage caused to him. However, magically powered objects like Jack's sword are very disruptive to his healing factor.
  • The Heavy: Aku provides the opening narration of each episode, summarizing the premise and often being the Big Bad behind each obstacle that Jack must overcome. He claims to be the embodiment of all evil and often gives Exposition for other characters' Back Story.
  • Hero Killer:
    • In "The Birth of Evil", he slaughtered most of the soldiers serving under Jack's Father. He also made Jack's Father and Mother both die as old slaves, deprived of adequate food and water under Aku's reign. He's also defeated a multitude of other heroes during his reign, with a few being directly shown.
    • In "XCVI", he nonchalantly kills the Scotsman after the latter attempts to invade his tower with an army. Of course, it doesn't stop the celtic hero from coming back as a ghost, however.
    • "C" reveals he killed the Guardian at some point. Unlike the Scotsman though, he doesn't come back.
  • He's Back: After spending most of Season 5 Out of Focus due to being in a depressed funk over Jack's immortality, Aku's old fire returns with a vengeance when he learns that Jack has lost his sword. Then it's quickly subverted when he sees that Jack has regained the sword by this point. Then it's Double Subverted when he realizes that Ashi is his daughter, and uses her to force Jack into a surrender.
  • Hijacked by Ganon: It's revealed in "XCVII" that he was behind the cursed wishing well from "Jack and the Three Blind Archers".
  • Hoist by His Own Petard:
    • Aku unintentionally rendered Jack immortal by sending him forward in time, so Aku has to physically defeat him somehow if he wants peace; simply waiting for him to die isn't an option, which Aku discovered by trying just that. Now Aku is a Nervous Wreck due to having run out of ideas to kill Jack with and being faced with the prospect of the threat of Jack's sword hanging over his head for eternity.
      • His subsequent despondence and depression over this causes him to stop spying on Jack. So he never notices that Jack lost his sword following their last confrontation, and that therefore Jack is powerless against Aku. Aku only learns of this after Jack reclaimed his sword.
    • Awakening Ashi's powers allowed her to use his abilities against him when she regained control - including his time travel power, which she uses to take Jack back in time and destroy past Aku, erasing him from existence.
    • Broadcasting Jack's execution only ensured that everyone Jack saved would show up to rescue him.
    • Visiting the Cult of Aku in the first place and leaving behind his essence to humor them with is ultimately what did him in, as it resulted in creating Ashi - the one who would successfully send Jack back in time to kill him.
    • All the way back in episode 1 Aku declares that nothing, not even Jack's Sword has the power of righteousness to kill him permanently. After sending Jack into the future, his sword is eventually further empowered with Jack's own righteousness and does have the power to kill him permanently. None of this would have happened if Aku simply let himself be sealed again and waited for a less able foe.
  • Holy Burns Evil: Jack's divinely-forged sword causes him horrible pain with even the slightest cuts and ultimately completely destroys him in the end, and he's shown to be vulnerable to other divine powers and forces, such as the Water Goddess in "Jack and the Gangsters".
  • Hope Crusher:
    • He could easily destroy all the world's time portals whenever he wants, but he usually waits until Jack is about to use one before doing the deed, just to torment the hero. He nearly succeeds in crushing Jack's hopes by destroying the last time portal and causing Jack to lose his sword, though this is subverted when the latter reclaims the sword and when Ashi creates a time portal.
    • He tries to be this in the finale of Season 5. After capturing Jack, he broadcasts it to the whole world, declaring his intent to publicly execute Jack in order to completely crush everyone's hopes. It backfires; instead, everyone Jack has ever helped mounts an all-out attack on Aku's fortress to save him.
  • Horns of Villainy: Aku's preferred form features enormous horns all around his head, resembling stag antlers, tree branches or, in line with his Japanese-inspired Oni-mask-like face, the crest of a shogun's helmetnote . Whenever someone constructs a tribute or statue of Aku, these are always prominently displayed.
  • Humanoid Abomination: While his default form is a borderline example as he keeps a vaguely humanoid, gigantic shape that can change to anything he wishes, any human disguise he assumes plays it straight: since his forms are limited to green/red/black colors, he looks mostly as a green-skinned human whom animals can detect the evil aura he emanates and reflections reveal his true appearance. He also still has access to any of his powers in human form.
  • I Control My Minions Through...: Depends on the minion, but he has a large number of sapient minions because he pays really well and he lets his people indulge all manner of horrific actions. He also has a few who worship him as a deity.
  • Immortals Fear Death: He was born from the primordial darkness of the universe, he's older than any mortal, and his rule over Earth has been going on for easily thousands of years. As a result, the only thing that consistently gets a rise out of him is the one weapon that can kill him, Jack's sword. After 50 years in the future, Jack finally succeeds in returning to the past. Future Aku's reaction is absolute horror, knowing he's about to cease to exist and there's nothing he can do about it. Past Aku spends his last few minutes running for his life from the 50 years stronger and more experienced Jack, a look of terror on his face.
  • Invincible Villain: The only weapon that can harm him is Jack's sword, and he's already won by the beginning of the series, taking over Jack's homeland. While Jack manages to defeat him in their first fight, Aku survives by sending him to the distant future before Jack can finish him off; by the time he returns, Aku has completely conquered the world. Throughout the series, Jack repeatedly manages to best him, but Aku always manages to escape and live to fight another day. It takes Jack coming back to the past literally seconds after Aku originally sent him to the future after their fight and he's at his weakest can Jack finally end him for good.
  • Irony: His ability to create time portals, the very same ability that sent Jack to the future, is used by his own daughter Ashi to return Jack to the past.
  • It's All About Me: For Aku, the only thing that matters is himself and a universe centered on himself.
  • Jerkass Gods: As the God of Evil, Aku feels nothing but contempt for all mortal lifeforms, callously and casually killing or otherwise abusing them for his own amusement. It makes one wonder why we see even one religious cult that worships him out of genuine devotion instead of fear.
  • Jerk with a Heart of Jerk: Whenever he seems to have a remotely soft side, this is always subverted because of his ego, sadism and cruelty. Because of course, he is literally pure evil after all.
    • This is best shown when when two of Aku's demon guards bring him some special prisoners they arrested: the alien prince and princess of a distant world. When the princess explains how they're trying to save their own planet from invaders, Aku sarcastically remarks "What a sad story!" with fake compassion, before sentencing them both to enslavement for life.
  • Kaiju: He's a giant monster who just happens to be from Japan, and is introduced by burning down tall buildings.
  • Karma Houdini Warranty: After spending the series avoiding punishment for bringing ruin and misery to the world, the final episode has Jack finally kill him for good.
  • Karmic Death:
    • Aku meets his end when the daughter he turned into a living weapon and tried to kill Jack with takes Jack back in time, allowing him to destroy Aku's past self and erase him from existence.
    • Past Aku is killed when Jack returns from the future 50 years stronger and more experienced, allowing him to annihilate Aku. Doubly so as Aku dies exactly the same as the many innocents he killed: terrified for his life against a foe so much stronger than he is that there is nothing he can do about it.
  • Kick the Dog: Really likes doing horribly cruel things just to prove what an asshole he can be. He never stops.
    • Outside of his need to back-stab everyone, blackmail is a routinary occurrence in his kingdom, as well as one of his most despicable actions. Good examples of this are episodes "XLIV" and "L". Similarly, both episodes ends up with disturbing implications.
    • In "Jack and The Lava Monster", Aku had attacked and decimated the land of a respected warrior. Even as the villain decimated all his fellow warriors and loyal subjects, the man bravely fought against Aku, ready to battle for the last time and die as a warrior. However, as punishment, Aku instead encased the man in an unbreakable crystal and forced him to watch as he slaughtered everyone he loved and destroyed his beloved kingdom, finally placing him within the depths of a mountain, refusing to grant him a warrior's death.
    • A great example of Aku's unnecessary cruelty was in "Jack and the Flying Prince and Princess". Princess Verbina respectfully introduces herself, her brother and Chitron to Aku. She tells Aku that their planet is under attack and they need reinforcements, and they ask only time enough to repair their vessel. Afterwards, Aku pretends to have sympathy for the prince and princess's plight before he has their ship confiscated and has them put in irons to be taken into the labor mines for the rest of thier lives. Chitron futilely tries to reason with Aku, but Aku cruelly just crushes the robot. And Aku did all this simply because he could.
    • In Season 5, was when he dragged Jack out of the last time portal and destroyed it, taunted in him while he was in a violent rage, and turned the little rams that led him to the portal into monsters for Jack to have something to kill.
    • On another occasion he disguised himself just to accompany Jack on a quest, find a magical artifact Jack could use to return home, and destroy it at the last instant purely so he could mock Jack.
    • Pulls a major one in the comic story "Jack and Jill". Aku disguises himself as a mute Combat Hand Fan-wielding geisha woman who Jack names Jill. They travel together for entire seasons, with Jack getting closer to her as time passes, until he suddenly discovers she's really Aku. Yes, not only did Jack fall for this trick again, but the relationship lasted longer than with Ikra. When asked why, Aku stated it was to teach Jack a lesson that no matter what,Jack will always be alone. What's worse, unlike with Ikra, where he was tricking Jack into leading him to a time portal, Aku had no reason to do it other than for his own amusement. Jack is so distraught, he can't even summon the energy to attack Aku. He just falls to his knees in despair as Aku flies away.
  • Kick the Son of a Bitch:
  • Killed Off for Real: Inevitably so in the series finale, "Episode CI," where Jack manages to travel back to the past and finally destroy Aku before he ever comes to power.
  • Know When to Fold 'Em: Whenever he gets into a fight, he goes at his opponent with everything he's got (if they prove an actual threat to him, of course). But when he realizes the fight isn't going in his favor, he panics and runs away.
  • Knight of Cerebus:
    • A Zig-Zagged example. In some episodes, such as "The Beginning" three-parter, "Jack and the Lava Monster", "Jack and the Ultra-Robots", "Jack vs Demongo", "The Princess and the Bounty Hunters", "Tale of X9" and "The Birth of Evil" two parter, he's every bit the embodiment of evil he claims to be. In other episodes, he's a complete clown with some hilarious lines. Basically, depending on the episode, he can make you laugh or scream. Sometimes both in the same episode.
    • Even his confrontation with Jack when he destroyed the last time portal was one of his darkest moments. Aku drove Jack to anger, transformed the three little rams into monstrous beings, and forced Jack to kill innocent beings in anger. Since this event, things went downhill for Jack in the next 50 years.
    • This is perfectly demonstrated in the penultimate "Episode C". In the first half of the episode, Aku is mostly portrayed in a comedic light, with him and Scaramouche doing a Happy Dance at the news that Jack lost his sword. Even his murder of Scaramouche for giving him outdated information is mostly Played for Laughs. However, it all quickly goes to hell once Aku finds out Ashi is his biological daughter and he takes control of her body to force her to fight Jack. Jack cannot bring himself to kill Ashi and surrenders himself and his sword to Aku. In other words, despite being portrayed as a joke for 70% of the episode, in one scene, Aku managed to bring the series to its lowest point.
  • Large and in Charge: Rules the world and has a Shapeshifter Default Form that is usually several stories high at the least.
  • Large Ham: So hammy that one of the first things he makes his slaves do is build statues of him. His manner of speaking (as demonstrated by the opening intro) is also based on traditional Japanese Kabuki, which comes across as hammy when translated into English. It's to the point that it's actually more jarring in the few moments that he's actually more subdued, such as in the Demongo episode.
  • Laughably Evil: He's a pretty funny guy, whenever he isn't performing any genocide, slavery, or treachery. Varies depending on the episode, there are some that present him as legitimately evil and a threatening figure. Or sometimes a bit of both. It's implied in part to be a result of having no other character trait besides pure evil - including any sense of restraint, which results in him being very whimsical, too self-absorbed to care about appropriateness and will hold grudges very easily.
  • Laughing Mad: He loves laughing maniacally.
  • Leaning on the Fourth Wall: In the episode "Jack vs. Aku", he makes this statement regarding his episodic encounters with Jack:
    Aku: "You'll swing your sword, I'll fly away, and probably say something like, 'I'll be back samurai!', and then I'll flutter over the horizon and we won't see each other for about a week. And then we'll do the same thing all over again!"
  • Let's Fight Like Gentlemen: In the episode "Jack vs. Aku," he proposes a one-on-one duel with Jack, with two conditions: Jack can't use his sword, and Aku can't use his superpowers. Aku holds his own for a while, but when Jack has him on the ropes, he quickly cheats, snatches Jack's sword, and tries to break it, only to find himself Out-Gambitted when the sword he breaks turns out to be fake; Jack was smart enough to anticipate that Aku would eventually break the rules, and thus stashed fake swords all over the place as decoys.
  • Leitmotif: His main theme sounds like low, malevolent, and warbling horns; with a few rattling flutes, and Scare Chords thrown in for good measure. It's barely even music, and strongly underlines the fact that despite his sometimes quirky antics, Aku remains the embodiment of evil. He also has an "action" theme which is heavy on taiko drums and eerie bells, fitting for a Japanese demonic overlord.
  • Little "No": In sharp contrast to his usual expressive and theatrical behavior, Aku lets out a yelp when he sees Jack and Ashi jump back into the past.
  • Locked Out of the Loop: After destroying every time portal, he no longer keeps watch over Jack. He's not even aware Jack lost his sword. Even after Jack retrieved his sword later on, he still remained none the wiser.
  • Long Game: Attempted during the 50-year Time Skip between Seasons 4 and 5. After failing to kill Jack time and time again, Aku destroyed every source of time travel on Earth and then retreated to his lair, planning to just wait Jack out until he died of old age. Sadly, due to an unexpected side effect of the spell he originally used to send Jack to the future, Jack is now The Ageless.
  • Lovecraftian Superpower: A trait he inherited from the Black Mass. Any kind of body horror, physical manipulation, shapeshifting, and dark magic is at his disposal as he is the embodiment of evil. The bit of himself he gave to the Cult of Aku, when drunk by the High Priestess, caused her to become pregnant and give birth to seven daughters, all of which carried Aku's essence inside him. Aku is able to take direct control of them and, by adding some more of his power, turn them into Humanoid Abominations.
  • Luke, I Am Your Father: In the penultimate episode, it's revealed that the seven Daughters of Aku (including Ashi) are literally his daughters, and not just members of a random fanatical cult dedicated to him.

  • Made of Evil: He's a fragment of an Eldritch Abomination who roamed across the cosmos. Aku's substance is flexible, strong, pitch-black, capable of re-sealing after most injuries, and has an extremely horrible effect when taken internally. It's Evil.
  • Make Me Wanna Shout: Aku can use loud screams powerful enough to damage the landscape as a form of attack.
  • Master Actor: A very helpful talent when you're a shapeshifter. He demonstrates this best when disguised as "Ikra", going far to depict himself as a heroine with a vendetta against Aku.
  • Meaningful Name: The word "aku" means "evil" in Japanese. It's also worth noting that he's the only major character in the series who goes by his (original) name.
  • Me's a Crowd: As part of his shapeshifting abilities, Aku can create multiple copies of himself. When fighting Jack's father, he splits himself into multiple duplicates of himself and possesses the armor of fallen soldiers to create a literal army of himself. This gets Played for Laughs in Season 5 where it's revealed that he secretly talks to a psychiatrist who is really another clone of himself. It's as hilarious as it sounds.
  • The Mirror Shows Your True Self: It's shown in "Jack and the Swamp Monster" that any reflection will reveal himself while he's in a disguise.
  • Mood-Swinger: One of his most jarring traits. One moment, Aku could be a hilarious Comic Relief and be a bad guy you simply Love to Hate, but the next he could be a heartless monster who would massacre innocents, enslave billions, and torture a man and make him see his whole life burn in front of him just for the fun of it (ie: The Lava Monster).
  • Mook Horror Show: Both Akus spend the last few moments of their existence terrified because they know their end is near. Past Aku is more pronounced, as when it becomes apparent he's zero match for Jack now, he desperately tries to escape as Jack hacks away at him, a horrified look on his face.
  • Mook Maker: Aku has the ability to make mooks from the same substance he's made up of, as shown in "Episode I: The Beginning" and these same mooks appear in "Jack and the Flying Prince and Princess"
  • Morphic Resonance: He always has the same black, red and green color-scheme in every form he takes.
  • Names to Run Away from Really Fast: His namely is literally "evil" in Japanese.
  • Narcissist: He once said "No mortal can defeat me" right before getting his ass handed to him, asked for a group of fish people to build statues of him every month, and sees Jack as foolish for even trying to fight him. The main impetus of the episode "Aku's Fairy Tales" is that he can't stand that children would rather worship Jack and not him and he attempts to win children over through fairy tales.
    Aku (from "Jack and the Flying Prince and Princess"): "I am Aku! This world is Aku and EVERYTHING IN IT IS AKU!"
  • Near-Villain Victory:
    • In "Jack and the Zombies", Aku steals Jack's sword and eventually catches Jack himself - and if not for being unaware that the sword couldn't hurt the innocent (like Jack), he'd have won.
    • After destroying the last time portal, he doesn't bother scrying on Jack. If he did, he would have realized his archnemesis lost his sword and the series would have ended there.
    • If Aku hadn't taken so long to figure out how he wanted to kill Jack in the series finale, he also would've won.
  • Nervous Wreck: In Season Five, while he outwardly displays apathy towards Jack, in private he's deeply frustrated by the fact that Jack can no longer die of old age that is helped by the fact that he doesn't know that Jack has lost his sword to the point that he secretly relies on a psychiatrist in the form of himself. All it took to get him out of this was for Scaramouche to deliver the news that Jack lost his sword.
  • New Powers as the Plot Demands: It's not really clear how far his abilities extend, and he's shown to be capable of dozens of powers, from shapeshifting into any size or shape, breathing fire, shooting energy beams from his eyes, is able to instantly teleport himself and others anywhere in the universe, the power of flight, telekinesis, making rips in space-time, creating sapient minions, is completely immortal, can quickly regenerate from any wound, can "corrupt" places and people, separate himself into multiple individuals, and can also see almost anywhere on Earth whenever he wants.
  • Nice Job Fixing It, Villain!:
    • Season 5 reveals that Jack's ageless nature is due to Aku sending him to the future. Aku later decided to destroy all known time portals to deny him all hope of returning home, but while this is debilitating to his nemesis, his immortality has ensured that Jack could potentially be a thorn in his side forever.
    • Aku is indirectly responsible for Jack's depression in Season 5, as well as his motivation to get back to fighting him. If Aku would have never visited the Cult of Aku, Ashi would have never been conceived. If Jack would have ended up facing those alien children from Episode 5 without the aid of anybody (i.e. Ashi), he would've had no idea that the alien children were still alive, therefore he would've successfully killed himself.
    • His awakening of Ashi's dormant Aku side allows her to, after breaking free of his control, send herself, Jack, and the sword back in time to before his evil could spread and destroy him for good.
  • Nigh-Invulnerability: Demonstrated whenever we see anything besides Jack's holy sword or other divine/magical attacks being used against Aku. Any conventional weaponry or mundane forms of attack can't even scratch him.
  • Nightmare Fuel Station Attendant: He manages to bring us a fair share of Nightmare Fuel in "The Premiere Movie". His hissy Creepy Monotone, his lack of humor and absolute sadism and cruelty...
  • Ninja Pirate Zombie Robot: Aku is a Lovecraftian, godlike demon from outer space. He's also a Sorcerous Overlord, Galactic Conqueror, and God-Emperor all rolled up into one.
  • No-Nonsense Nemesis: Despite his Stupid Evil tendencies, Aku has displayed this on occasion.
    • In the pilot episode, immediately after breaking free from his imprisonment, Aku's first order of business is to attack the village, massacring everyone. When Jack's father tries to get the sword, Aku immediately grabs him.
    • In "Jack and the Zombies", once Aku gets Jack's sword, he wastes no time in attacking Jack, immediately going on the offensive and forcing Jack on the defensive throughout the episode. He doesn't stop to gloat or banter and gives Jack little time to breathe.
    • In "C", as soon as he finds out Jack has lost his sword, he immediately teleports to where Jack is and prepares to kill him after taking a moment to rub the situation in his face... until Jack reveals he's retrieved the sword, which nearly makes him scram, until he realizes something interesting about Ashi...
    • When Jack said Aku destroyed every time portal, he meant every time portal, including the one protected by The Guardian.
  • Not Me This Time: Jack initially assumes that the Daughters of Aku were sent after him by Aku. In truth, Aku had no idea the Daughters existed. He has a very passing memory of the cult they came from, and didn't realize the High Priestess drank the essence he left until years after the fact.
  • Not-So-Harmless Villain: Aku's initial appearances in Season 5 show him in a comedic depression over his inability to kill Jack. Then the audience is reminded that he's unstoppable without Jack's sword, as he effortlessly annihilated the Scotsman's army, and then killed him personally (though he immediately got better). It's later revealed that he killed the Guardian and destroyed his time portal, both defeating the only person in the whole series Jack had ever lost to and seemingly revoking Jack's status as The Chosen One.
    • Later, in a flashback prior to the Time Skip, we also see that he was responsible for Jack losing his sword and his depression, as a wake up call that for all his humor, he is still the living embodiment of evil.
    • In the penultimate episode, Aku learns that he is Ashi's biological father through his essence, and possesses her to fight Jack, knowing that Jack would never harm someone that he cares about. The episode ends with Jack kneeling in surrender as Aku holds his sword in triumph.
  • Obviously Evil: Right down to his name!
  • Offing the Offspring: After Ashi breaks out of his control, he attempts to kill her, but fails when she uses his powers against him.
  • Oh, Crap!: In the Grand Finale, when Ashi uses his powers to send Jack and herself back to the past, Aku instantly realizes he's done for. Past Aku has one of his own when Jack returns.
  • Omnicidal Maniac: Aku taken billions of lives in all his existence, so this is to be expected.
  • One-Man Army: Aku has destroyed countless armies all by himself. Nowadays though, he's grown lazy enough that he relies on robots to do the conquering for him, and hires bounty hunters for other dirty work.
  • OOC Is Serious Business:
    • His depression as of Season 5 is incredibly jarring considering his Laughably Evil shtick.
    • When he realizes that Ashi and Jack have traveled back to the past to destroy him, he loses his usual demeanor and can only summon a small "Oh no.".
  • Opportunistic Bastard: Throughout season 5 Aku has hiding away from the outside world and hasn't bothered to keep up to date with current events. As such, he was completely unaware of Ashi's existence or her status as his daughter. Once he realizes this, however, and once he realises her and Jack's mutual feelings for one another, he wastes no time in manipulating his essence inside Ashi to break Jack's will and steal his sword.
  • Orcus on His Throne:
    • Justified. The entire premise of the show started because Jack could defeat him, so Aku actively avoids facing him himself, unless he's gained some advantage that he's sure will let him win. "Tales of X9" also revealed that the entire reason he relies on an army for conquests is because he found taking over the world on his own was going at too slow a pace for him.
    • In Season Five, he managed to destroy all known time portals and planned on simply waiting for Jack to die of old age. Unfortunately for him, he didn't realize that thanks to his time magic Jack no longer physically ages. With this last, surefire attempt at finally killing Jack failing, Aku's just too depressed to fight him now.
  • Out of Focus: In Season 5 he appears very sporadically despite being the second major character after Jack. Justified in that he's in a state of depression over his stalemate with Jack and he sees no point in doing anything.
  • Our Demons Are Different: Aku is an unearthly and unholy being spawned from a primordial darkness.
  • Overarching Villain: Basically, he is the catalyst for the whole series.
  • Paper-Thin Disguise: Due to Morphic Resonance, it is often easy for the audience to tell that someone is just Aku in disguise. Jack is sometimes taken in, sometimes not.
  • Past-Life Memories: Not consciously but more on an instinctive level. The Black Shadow that Aku came from was a vast ever changing shape of darkness that wanted to eat/absorb everything in the universe. It may or may not have even been aware possibly making it an Almighty Idiot. Certainly it had the ability to devour Odin, Ra and Vishnu but seemingly had no skill or reasoning ability to use tactics and cunning. The piece of it that eventually became Aku was slowly growing and absorbing the earth before the magic arrow Jack's father hit it with to destroy it instead condensed it into a single form and apparently granted it self awareness. Aku's desire to dominate and rule over everything would be an extension of the hunger to eat everything that the entity he was once a part of had. Further, him being crafty and tricky could be based on how Ra, Odin and Vishu ripped him apart when the Shadow tried to fight using only force and how Aku, seemingly on an unconcious level, took the lesson to avoid danger to heart. After all, if it had been Aku the three gods faced having the same size and power the Shadow had, there's a good chance they would have lost.
  • Person of Mass Destruction: Aku is more than capable of destroying the world on his own.
  • Pet the Dog: A partial example. As a tyrannical monarch, Aku is pretty casual with those who respect him. Of course, this isn't saying much, considering he still sees you as inferior or a subordinate.
    • There has only been one time that Aku has ever come close to this trope that wasn't part of a disguise (i.e. when he was disguised as Ikra or the wizard) or some part of a greater plan that ultimately benefited him or his ego (such as trying to get kids to like him with a personal storytime or blessing the Daughters of Aku with some of his essence because their worship pleased him). After Scaramouche delivered the (unknowingly outdated) information about Jack having lost his sword, he used his magical eyebeam powers to give Scaramouche his body back and then performed a Happy Dance with him in celebration. Unfortunately for Scaramouche, he made the mistake of saying "I'd bet my life on it" and either took a ride with Aku or Aku insisted he come with him. After that, well... let's just say that Aku wasn't too happy to see Jack with his sword again and Scaramouche was punished accordingly.
  • Phrase Catcher: Jack tends to yell out "AKU!" whenever they meet.
  • Physical God: He's an immortal, divine demon with immense magical powers, and he can only be killed by the power of other literal Gods like Ra, Odin and Rama.
  • Pitiful Worms: In the Grand Finale, he outright calls Jack's allies "insignificant insects."
  • Playing with Fire: He can toss blue fireballs at opponents, or incinerate them with his Eye Beams.
  • Plucky Comic Relief: Oddly enough, despite being the Big Bad, his Laughably Evil tendencies make him a main source of levity, especially in the otherwise Darker and Edgier Season 5.
    • Of course, this trope is monstrously averted in "C" and "CI".
  • Post-Final Boss: Past Aku is barely a threat when Jack kills him, which is justified since Jack catches him off-guard after he barely survived his duel with Past Jack. The corrupted Ashi essentially acts as Jack's Final Boss, with Future Aku, exponentially stronger than his past self, serving as the Final Boss for Jack's allies.
  • Practically Joker: He's a horrific sadist, a manipulative sociopath, and a homicidal maniac who enjoys killing and torturing people For the Evulz; and he especially enjoys tormenting his Arch-Enemy (The Hero, who is his absolute antithesis). While Aku is funny, bombastic and Faux Affably Evil, his Arch-Enemy is a serious, devastated, honorable man with serious anger problems. Aku is practically The Joker in the form of an Eldritch Abomination.
  • Praetorian Guard: In addition to his Mecha-Mooks, Aku maintains a legion of his rarely-seen demonic minions from the pilot episode and "Jack and The Flying Prince and Princess". As shown in the latter, they serve as sub-commanders of beetle drone squads. However, they're the weakest of his minions, and disappear in puffs of smoke when defeated.
  • Psychopathic Manchild: For an ancient and powerful demonic overlord, Aku is ultimately rather petty and immature. His motivation for trying to conquer the universe is simply to have fun, all the while treating everything with a dark sense of humor. Not to mention that he easily gets bored or irritated when things aren't going his way.
    • "Jack vs. Aku" examines his behavior further; while Jack believes that fighting Aku is his life's mission and treats it with the utmost seriousness, Aku considers every battle with Jack to be some kind of game (a game that's gotten a bit too long and repetitive for him). So Aku wants to shake things up by challenging Jack to a duel, but this time they have to fight differently.
    • In Season 5, we discover that Aku's inability to kill Jack for the past 50 years has driven him to depression, but he comes off acting like a teenager or young adult who's simply become bored and confused about what to do with his life. In contrast to Jack, whose depression seems much more justified, because his whole life has been mostly full of tragic events.
  • Pyromaniac: Aku played this trope in the darkest way possible. He's a monstrous arsonist who enjoys destruction and murder purely for its own sake.
  • Pyrrhic Victory: Season 5 reveals Aku succeeded in destroying all the time portals, leaving Jack trapped in the Bad Future forever. The problem is that Jack has become The Ageless and Aku has realized he trapped himself in a stalemate with Jack for apparently eternity. Now Aku just stays moping around in his lair and having therapy sessions with himself.
  • Rape, Pillage, and Burn: Aku doesn't seem to have any other hobbies outside of wiping entire civilizations just for the heck of it.
  • Red Baron: He has several fear-inducing nicknames (apparently self-given, though other characters use them occasionally) including "Master of Masters", "Shogun of Sorrow", and "Deliverer of Darkness".
  • Reality Warper: To the point that Aku can make it rain treasure, or trap Jack in a pocket between time.
  • Really 700 Years Old: Aku (as a sapient being) has existed for hundreds or even thousands of years. Though the primordial darkness he was spawned from is far more ancient than him.
  • Red and Black and Evil All Over: His entire body is black, his flaming "eyebrows" are red, and he's the Big Bad.
  • Ret-Gone: Jack is taken back to the past by Ashi and kills Past Aku, altering history so Future Aku and his reign of terror never existed.
  • Sadist: Aku thrives on the suffering of others.
  • Sanity Slippage: In Season 5. After 50 years of battling Jack, Aku became mentally broken and depressed... until "Episode C".
  • Satanic Archetype: He is the living embodiment of evil, and is so powerful and monstrous that almost everyone fears and loathes him, including other villains. His conquest of the world seems to be a direct parallel to the apocalypse, and the Pit of Hate seems to be a parallel to Hell. Season 5 seems to emphasize this point further, since there is an evil cult that worships Aku and treat him as a deity.
  • Schmuck Bait: Aku distributed lots of "magic" around the world - time portals, wishing wells, secret magical or technological weapons. They're always Schmuck Bait.
  • Screaming Warrior: He often lets a scream before a fight and often lets out a scream of frustration when he begins to lose.
  • Screw Destiny: A rare villainous example. Jack was apparently destined to become the Chosen One and use the Guardian's time portal, but Aku destroyed it before that could happen.
  • Screw This, I'm Outta Here!: In "C," Aku tries to beat a hasty retreat after realizing Jack has already reclaimed his sword, but something else catches his attention before he leaves.
  • Sealed Evil in a Can: Jack's father defeated him by sealing him away inside a tree instead of killing him. The first episode shows him breaking free and taking his revenge.
  • Self-Mutilation Demonstration: When fighting opponents he considers weak, he often lets their attacks hit him just to show the futility in actually harming him. This backfired twice when Jack's father and later Jack showed up with the sword, since it can actually hurt him.
  • Shapeshifter Default Form: He usually appears as a tall, shadow-like being with a green face, fangs, spikes protruding from both sides of his head, as well as eyebrows and a goatee of flame. Due to his origin it's hard to say if he's Type A (this is his true form) or Type B (it's the form he prefers to take on when not using his shape-changing abilities to fight or disguise himself).
    • A little more basic, before he was given sapience or when he was sealed away, he takes the form of a barren black tree, and he causes the land around him to go dead and grey.
  • Sizeshifter: A natural extension of his shape-shifting ability, and in his default form he's usually gigantic. He tends to shrink whenever Jack's sword hits him, though, but if left alone long enough, he will regrow to his original size.
  • Slasher Smile: Right as he is about to stab Jack with his own sword in "Jack and The Zombies", he sports a sadistic smile with crazy eyes.
  • Slavery Is a Special Kind of Evil: He is a depraved monster who has enslaved entire nations and races. He doesn't care if his slaves die of fatigue or thirst, and much like other evil things he has done, this one is played in the darkest way possible.
  • Slouch of Villainy: A variation; when annoyed or coping with a recent defeat, Aku tends to sink low in his throne with his shoulders raised, looking like a grumpy old man in an armchair.
  • The Sociopath: Despite being a demon that is literally made of pure evil, Aku has the classic traits of a psychopath. He is exceptionally adept at putting on a good facade of trust; He is entertaining, bombastic and funny (superficial charm), he possesses an inordinate attitude of superiority and grandeur, destroys cities and commits crimes to satisfy his sadism and tendency to boredom, is a pathological liar who frequently deceives and manipulates for personal gain, or even For the Evulz; He's incredibly aggressive with things related to his ego, and perhaps most importantly: he possesses an incredibly high criminal versatility, with atrocities that could take up more than one sheet, which is quite common in sociopaths/psychopaths.
  • Sorcerous Overlord: Aku has many powers of dark magic, which he has used to conquer and rule the world. And now he seeks to expand his empire across the galaxy.
  • The Soulless: As a demonic being and an absolute monster who's Made of Evil, he doesn't have a soul and that's one of the main reasons why the only way to end him is to cease him from existence forever.
  • Spikes of Villainy: His head is covered in branch-like horns and whatever form he takes tends to have a spike on each joint.
  • Stepford Smiler: Aku in Season 5 has been reduced to this. Outwardly, he portrays himself to his followers as being completely apathetic towards Jack. Privately, he's reduced to a sad puddle of his former self, wracked with anxiety over the fact that every attempt to kill Jack, even by old age, has utterly failed and faces uncertainty about the prospect of being locked in an eternal stalemate with his arch rival.
  • Stronger with Age: Not inherent within his makeup exactly, age nature or longevity don't make him stronger, but rather time allows Aku the opportunity to pillage resources and mystical sources of power that would allow him to augment his own considerable power. This was exactly the reason Aku sent Jack into the future. The trip was only an instant for Jack but for Aku it was the same as exiling his enemy for thousands of year while Aku used the time to build an empire, gain resources and enhance his own personal might.
  • Stupid Evil:
    • He abuses Mooks, cheats those who strike bargains with him, or just spends too much time gleefully torturing Jack when he could easily crush him in an instant. Jack's very existence is owed to this happening time and time again.
    • He does get his comeuppance in regards to this at times. One example being his deal with the Imakandinote , and his Hermit disguisenote .
    • Even his minions are prone to this, although this is a given when he orders them up like a normal person would order for take out.
  • Suddenly SHOUTING!: He tends to overemphasize whenever referring to the samurai's refusal to DIIIIIIIIIIIIIIIIE!
  • Superpower Lottery: Aku uses a large variety of magical abilities, which sometimes seem to just come out of nowhere. They include, but are not limited to: immortality, shapeshifting, heat vision, telekinesis, super strength, super speed, flight, teleportation, and even creating time portals.
  • Super Strength: Even if he scales down to human size for some reason, he has superhuman strength. This seems to diminish, though, if he scales down into several human-like forms.
  • Supervillain Lair: Aku is rarely seen outside of his lair, which is little more than a large chamber filled with a forest of seemingly-stone pillars stylized to look like flames. Aku needs and keeps only a few amenities, including a magic viewing screen, a balcony to admit visitors and petitioners, and any other items needed for a one-off gag. In Season 5, we finally see it from the outside, which is a large, black, tree-shaped tower (similar to his original form) in the center of a crater. As it's made from him, when Jack finally kills him, it explodes along with him.
  • Surrounded by Idiots: In Jack Vs Aku, he realizes that most of his bounty hunters are incredibly incompetent, causing him to attempt a duel against the samurai. By Season 5, he's lost all hope that anyone will be able to kill Jack for him.
  • The Syndicate: It is revealed in Season 5 that Aku's regime welcomes outlaws, bandits, gangsters and evil organizations. Interestingly, most of the antagonists have connections to Aku, from lowly thugs to ruthless mobsters, assassins and slave drivers.

  • Takes One to Kill One: As a magical entity, Aku is immune to conventional attack and can only be harmed by magic. Divine magic in particular, such as Jack's sword, are his kyrptonite.
  • Take Over the World: He already has, but apparently it's not enough. So now he seeks to dominate the known universe.
  • Talking to Themself: In Season 5, he copes with his depression by having therapy sessions with himself to talk about Jack and his failure kill him, and how he has trapped himself in a stalemate with Jack for apparently eternity.
  • The Shadow Knows: When he shapeshifts, reflections of him, such as in the water, may give him away.
  • Third-Person Person: When he's being especially hammy.
  • This Cannot Be!: Had this reaction when Jack's father showed up with the sword and actually hurt him with it.
  • This Is Gonna Suck: Has a resigned but no less perturbed reaction when he sees Jack and Ashi travel through a summoned time portal and realizes he's screwed in the future and past.
  • Trauma Button: Jack has become a big one for him as of Season 5. When talking about his frustrations with his "therapist" (who's also himself), he cuts himself off upon mentioning Jack and assures himself that his lair is "a safe place". The Scotsman praising Jack after Aku destroys an attacking army is enough to kill off any enjoyment he might have gotten out of the act, such that he just slinks back to his lair and lets the Scotsman's daughters escape.
  • Troll: He was an absolute jerk who pulled a lot of cheap shots and jerk moves on Jack over the years.
  • Undignified Death: Aku dies fleeing Jack in pure terror like the Dirty Coward he is, so worn down between Past and Future Jack's assault that his 'final form' can best described as one of the Pacman Ghosts
  • Unskilled, but Strong:
    • Played with. Aku has shown on occasion that he is more skilled than he lets on as he is seen using weapons on occasion and is a surprisingly strong hand-to-hand combatant, but he relies mostly on his shapeshifting, his vast magic, and the fact few things can actually hurt him. One of those things being Jack's sword.
    • This is most shown and somewhat deconstructed in the aptly titled episode, "Jack Versus Aku". Aku challenges Jack to a final battle with only two rules: Jack is forbidden to use his sword and Aku is forbidden to use his powers. Though Aku manages to hold his own with just his Super Strength and hand-to-hand skills, Jack proves to be the better fighter and has Aku on the ropes, forcing him to break the rules to turn the tide.
  • Unusual Eyebrows: "GREAT FLAMING EYEBROWS!" Season Five shows that they are detachable and that he removes them when sleeping.
  • Victory Is Boring: In Season 5.
    • The past 50 years have technically been going in Aku's favor, even if his war on Jack isn't over yet. As a flashback reveals, Aku had destroyed all (known) time portals in the world, torments Jack over this, and leaves his enemy a depressed mess on the verge of attempting suicide. However, Aku can't enjoy his (temporary) triumph because Jack just won't die, and sooner or later he'll face Aku again.
    • Aku tries to get out of his malaise by massacring three armies, and then obliterates the Scotsman for calling him a coward. For him, it's gotten so mundane that it's a lot less fun than he thought it would be.
  • Vile Villain, Saccharine Show: A meta-example. While Aku isn't the first Cartoon Network Big Bad who's an absolute monster with no redeeming qualities (i.e. Katz), he is still one of the darkest Cartoon Network villains to date, which is quite impressive. He's a sadistic, genocidal dictator, with his crimes being heavily centered on mass murder, slavery, torture, Mind Rape, and other acts of inhumanly extreme cruelty. Compared to the more friendly, cartoonish, and laughable villains, Aku truly sets this series apart from Cartoon Network's other shows. No wonder why the final season of the series became part of [adult swim].
  • Villain Decay: In Season 5, he seems to have lost a lot of interest in killing Jack and has almost given up on combating him completely. It doesn't help that he's literally began to talk to himself and close himself off from his own followers. Justified in that, rather than not wanting Jack dead anymore, it's that he flat-out can't kill Jack—or at least that he's run out of ideas on how to do so—and therefore holes up until something changes that he can pounce on. This gets subverted with a vengeance in "Episode C", when he immediately goes after Jack upon learning the latter lost his sword—the only thing that can kill Aku (although he's ultimately too late to do anything with the info). Then, upon realizing Ashi's his biological daughter, he immediately possesses her and has her fight Jack, forcing the latter to kneel in defeat as Aku takes possession of Jack's sword.
  • Villainous Breakdown:
    • A gradual and humorous one in the episode "Aku's Fairy Tales". When Aku attempts to win over children from their Hero Worship of Jack by telling them fairy tales painting him as the hero, one of the kids requests a story about Jack. Aku gets angry, but quickly acquiesces, attempting to paint Jack as the villain. As the episode wears on, the children begin to poke holes in Aku's stories, frustrating him and forcing him to change up his stories until they become increasingly convoluted. Eventually, Aku hits his breaking point and teleports back to his lair, greatly annoyed.
    • In Season 5, post Time Skip, Aku has been reduced to sulking miserably in his lair and literally talking to himself (in the form of a therapist) about his complete inability to kill Jack, even by old age. He's completely apathetic to his minions and subjects bringing him tribute, and generally seems to have come down with depression.
    • Played with in the finale. His reaction when Jack and Ashi head back to the past through a time portal that the latter created is a subdued "Oh no". However, his expression tells a different story as Aku realizes that his end has come, and there's nothing he can do to stop it.
    • Played straight with Past Aku, whose reaction to Jack returning and completely overpowering him is to spend the last few minutes of his existence in complete terror, trying desperately to escape his demise.
  • Villainous Friendship: Seemingly with Scaramouche, but knowing Aku, this is definitely subverted. They shared a Happy Dance after the latter gives the good news that Jack lost his sword, only for Aku to blow his head up after thinking (mistakenly) that Scaramouche either fed him false info or outright lied to him. It seems Scaramouche really did think they were friends, considering he always gloated about being Aku's favorite henchman. Plus, would a being who's the ultimate embodiment of all evil even understand the meaning of friendship?
  • Villainous Harlequin: His perpetual hammy attitude, clownish monster-face and general air of having fun suggest this trope. Though it is, in some ways, a facade.
  • Villain Override: Can do this to Ashi, and anyone who has his essence, as she was conceived by the High Priestess drinking the essence of his that he gave to the Cult.
  • Villain Protagonist: Aku stars in a couple of his own episodes: "Aku's Fairy Tales" (which he narrates), and "The Birth of Evil (Part 1)" (though it eventually switches focus to Jack's father). Both episodes revolve around Aku, while Jack doesn't actually make a (direct) appearance in either of them.
  • Villain Respect: Downplayed. Aku doesn't actually respect anyone except for himself, but he acknowledges that Jack, at least while armed with his special sword, is a superior fighter and a dangerous threat whom he treats with the appropriate level of fear and caution.
  • Villain with Good Publicity: Downplayed. While many people know how evil and despicable he is, many are determined to kill his enemy (Jack) as a reward. Furthermore, he has a cult worshipping him out of genuine fanatical devotion.
  • Villains Out Shopping: He might literally be Made of Evil, and rule the world with an iron fist, but there are times when he needs to get his Evil Laugh ready, pick up the phone, and order a new henchman.
    Aku (On the phone): Yes, I can hold. (Sits complacently) Yes. I would like to place an order for delivery. Aku. I think I'm in the computer. YES! That's it. I'd like a large— what? Huh? EXTRA THICK!!! Thirty minutes or it's free? EXCELLENT!!! (Maniacal laughter which is cut off by the guy hanging up)
    • The opening to the second episode of Season 5 in a nutshell. Aku gets up, does his morning stretches, meets with a delegation of mud-people (and complains about them messing up his floor), blows off his scientists' latest beetle drone, and has a therapy session with himself.
  • Voluntary Shapeshifting: He can transform into pretty much anything, usually an animal but he can also change his shape to the point where he's outright formless, and even introduces himself as a "shape-shifting master of darkness" during the opening narration. To top it all off, he can shapeshift into a freaking storm.
  • Weaksauce Weakness: As mentioned above, despite being an ageless, powerful, and immortal demon, Aku is somehow vulnerable to viral diseases.
  • Weak to Magic: While not as noticeable as his weakness to divine powers or weapons, Aku tends to struggle more when faced with magical powers or weapons compared to his usual ability to flat-out No-Sell other mundane forms of attack. The Scotsman's Celtic Magic noticeably manages to counter his attacks and the Stone Samurai, an ancient magical giant, manages to actually hurt him.
  • We Have Reserves: Aku has sent wave after wave of robot minions after Jack over the years, even after it's become clear that none of them stand a good chance. In Season 5, he's stopped holding out hope that any of the robots will ever defeat Jack, and they're now commanded entirely by his scientists.
    Jack: "Aku keeps thinking that one of his machines can defeat me."
  • When Trees Attack: Despite the pliable nature of his black-matter body, Aku was actually spawned from a tree that was possessed by the fragment of a primordial evil entity that landed on Earth. This is evidenced in how when Aku moves, the sound of wood creaking can often be heard, implying he retained some of his original nature in his default form.
  • Would Hurt a Child: Aku plays around with this trope. But with his absolute ruthlessness, he definitely doesn't care about the age of any of his victims.
    • Aku has committed many genocides of countless nations, by massacring towns and enslaving the survivors. This would obviously include a lot of children, but we don't see them getting harmed on-screen.
    • In the second episode, a group of aquatic aliens come to him seeking shelter on Earth, due to having their oceans drained. Aku admits that he was the culprit, causing the alien leader's son to call him a monster. Aku promptly vaporizes him with his Eye Beams, but consoles the grieving father by telling him that the boy was teleported to the Pit of Hate (where he would likely be tortured and brainwashed until he learns "proper respect for Aku").
    • Aku also killed the Lava Monster's family when he attacked his kingdom, including his two young children.
    • In a later episode, he attempts to win over a group of children by telling them fairy tales. And despite being more than capable and having every reason to harm them for their Hero Worship of Jack, he never does. Why exactly he refrained from harming them is unknown, though it was likely more that he wanted to continue trying to brainwash them, rather than any moral reasons.
    • In "Jack and the Flying Prince and Princess", he's more than willing to enslave two innocent teenagers already devastated by war.
    • In addition to this, Aku's minions and bounty hunters hurt, torment and murder children on a daily basis and Aku himself doesn't seem to mind. In "XCII" the Beetle Drones decimated a village and tried to kill a little girl and her mother. Scaramouche made a habit out of massacring entire villages, children included, and he is still considered Aku's "favorite assassin". It is also shown that Aku welcomes criminals from across the galaxy and allows them to destroy and massacre populated villages that are explicitly shown to have children within them. In an old Cartoon Network game, "Desert Quest", Aku and his minions attack a village, badly injuring many of the villagers and nearly killing a young girl.
    • In a season 5 episode, an entire village of children are kidnapped and forced into a violent frenzy against everything around them. However, it's never specifically stated that this was on Aku's orders. The episode largely deals with coming to terms with Aku's effects on the world so it's a safe bet, but it's also worth noting that around this time Aku himself hasn't been doing much of anything.
    • In "Episode CI", Aku kills all of Jack allies when they arrive to rescue him by shifting a cloud that rains giant spikes on Jack's allies, including Rothchild's young grandchildren. That's right, Aku flat-out murdered children on-screen.
  • Yank the Dog's Chain:
    • Quite literally yanked a time portal away from Jack just as he was about to enter it. Much later, he yanks Jack through the portal and then destroys it to keep him from going back home.
    • Is on the receiving end of this when his apparent ultimate victory over Jack is torn away from him by an army of Jack's allies and Ashi, leading directly to his death. To make things better, his death in the past happens just a moment after he sent Jack to the future.
  • You Have Failed Me: The punishment for failing him is the mandatory death sentence:
    • His response to Demongo's defeat is to destroy him. He even says the trope name word for word. For some reason, he resurrects him in Season 5.
    • Scaramouche really asked for it when he bets his life on Jack being sword-less when he informs Aku. Aku is naturally annoyed to find out Scaramouche's information is outdated, and proceeds to casually destroy him.
  • Youkai: A nigh-omnipotent, malevolent, amorphous daiyōkai born from primordial chaos.
  • Your Size May Vary: Possibly justified given his shapeshifting, but even then his size varies from shot to shot. Most of the time, he's 5 times the size of a skyscraper, others he's only a few stories tall.

    Other Forms 

The Black Mass

A malevolent, primordial cosmic entity and the source of all evil. Before it can consume the universe, three deities (Odin, Ra, and Rama) arrive to exterminate this great evil. Before it was completely destroyed, a fragment of it escaped and crashed forcefully on Earth circa 65,000,000 BC. This is the original incarnation of Aku.

  • Almighty Idiot: This thing didn't seem to have any real mind or personality, until the Emperor shot a magic arrow that turned what was left of it into Aku, who was now a self-conscious yet still malevolent being.
  • Apocalypse How: Attempted to cause a Universal-scale one. The fragment that ended up on Earth could've potentially swallowed up the whole planet if it hadn't been turned into Aku instead.
  • Blob Monster: It was basically a giant puddle of living black goo.
  • Dark Is Evil: The true embodiment of evil indeed.
  • Diabolus ex Nihilo: While it serves as an explanation for how Aku came to be, we have absolutely no idea what exactly this thing is or where it came from; just that it once existed and almost destroyed the universe.
  • Eldritch Abomination: At least Aku has a comprehensible form, but this thing was an (almost) mindless blob monster.
  • Extreme Omnivore: It enveloped and devoured any creature that got too close.
  • Generic Doomsday Villain: It wanted to devour the universe, but was vanquished by Odin, Ra, and Vishnu, and it is the source of Aku. That's all we know of it.
  • Greater-Scope Villain: Of the whole series. It gave birth to Aku, but it's not involved in the main story.
  • Nigh-Invulnerable: It can only be destroyed by the power of the gods, hence why Aku has to be harmed with a divinely-forged sword.
  • No Name Given: As a mindless blob from outer space, it didn't really have an actual name or identity. Well, that was until what was left of it turned intelligent and took the name of "Aku".
  • Phlebotinum Killed the Dinosaurs: When its last remaining fragment crash-landed on Earth, it caused the extinction of the dinosaurs.
  • Posthumous Character: It was already destroyed by the deities, but is reincarnated as Aku.
  • Satellite Character: It merely serves as the source of Aku.
  • Time Abyss: This thing is at least millions of years of old, if not billions or even older.

Voiced by: Jennifer Martin

One of Aku's disguises, a beautiful woman who traveled closely with Jack while on a desert quest to find a magic jewel.

  • Bitch in Sheep's Clothing: Ikra fools Jack into believing that she's another wandering hero much like him, who just wants to save a loved one from Aku. Jack doesn't realize that his new friend is actually an old enemy until it's too late.
  • Contralto of Danger: She had a deep and husky feminine voice, which only highlights her ominous nature even further.
  • Dark Action Girl: Though Jack wasn't aware of Ikra's true dark nature, or that "she" wasn't actually a real girl, until Aku revealed himself at the end of "Jack and the Warrior Woman".
  • Dark and Troubled Past: Ikra fabricated a rather cliche-sounding backstory, claiming that she wants to save her father, who was taken hostage by Aku (much like Jack's dad in the past). Jack's natural sympathy makes him trust her, so they continue travelling together.
  • False Friend: Ikra makes herself seem like a new companion or even a potential love interest for Jack. This poor, lonely guy didn't realize that Aku was playing him for a fool until it was too late.
  • Foreshadowing: There are so many hints in that episode about Ikra's true identity, but Jack doesn't even see through them.
    • The fact that her color scheme matches Aku's almost exactly: black, green, and red.
    • When the shaman senses the "ultimate evil", his last line said to Jack, who thinks it was the robots, is "You don't understand!". After Jack and Ikra escape from Aku's robots, the robots simply stop their chase and close their eyes with satisfaction, aware of the trickery.
    • Later at night, a mouse eats food from Jack's hand, but is scared of Ikra and digs underground to run away. Also while Ikra is telling her (fake) story to Jack, she manipulates their campfire to help illustrate.
    • When the magic jewel tests Jack's and Ikra's hearts, it found out that Ikra is pure evil. The jewel's guardian mainly tries to fire its blasts at Ikra (besides Jack not wanting to fight). Ikra soon reveals that she can fly and become a giant to defeat the jewel guardian, much to Jack's (still oblivious) confusion. But Jack doesn't realize that he's been fooled until after Ikra smashes the jewel, cackles maniacally, and then changes back into Aku.
  • Gender Bender: The male Aku took on the shape of a pretty woman. This must've added an extra layer of shock for Jack, who was obviously almost feeling romantically attracted to "Ikra".
  • Green-Skinned Space Babe: Green-skinned woman in a sci-fi setting and conventionally attractive. Of course, it's really Aku in disguise.
  • Kicking Ass in All Her Finery: She wears a long and elegant black dress.
  • Obviously Evil: Her color scheme: black, green, and red should've been a dead give away.
  • Villainous Rescue: She introduced herself by saving Jack from some of Aku's robots, making it seem like an example of Big Damn Heroes.

The Hermit
Voiced by: Mako

Another one of Aku's disguises, as a short old man who wants Jack to find the Gems of Cronus so that he can revive the Titan.

Voiced by: Phil LaMarr and Mako

During one encounter with Aku (who was somehow infected with a flu), Jack accidentally swallowed some phlegm that Aku coughed out. The result was a terrifying transformation into a small clone of Aku, which could only be reversed by Jack fighting an internal battle of wills.

  • Achievements in Ignorance: Aku never intended to do this, causing it to happen by accidentally coughing on Jack when he was sick.
  • Battle in the Center of the Mind: Jack struggles but eventually manages to regain control of his body, and destroys the Aku parasite.
  • The Corruption: Getting a small piece of Aku inside him causes Jack to slowly become an evil creature as well.
  • Demonic Possession: The infection causes Jack's mind to slowly become an extension of Aku's.
  • Exorcist Head: When Jack's metamorphosis is nearly complete, he twists his head around a full 360°.
  • Fights Like a Normal: Despite his transformation, Jack still fights with his sword instead of using any superpowers.
  • Humanoid Abomination: Half-man and half-demon, with the latter half threatening to become whole.
  • Transformation Horror: Needless to say, turning into Aku is a very unpleasant experience indeed.
  • The Virus: Rather literally, as Jack's transformation was caused by a horribly mutated strain of the flu virus.
  • Zombie Infectee: Jack tries to hide his changing body as much as he could after he realized that he's slowly turning into a clone of Aku. Once he was nearly fully converted into an extension of Aku, he drops the act of hiding himself and destroys the lizard monks' time portal.

The Therapist
Voiced by: Greg Baldwin

Aku's psychiatrist, who is really a clone of Aku himself wearing glasses and a suit. Aku talks to him about his depression resulting from his inability to kill Jack.

  • Foil: To Inner Jack. While Inner Jack constantly insults Jack, trying to get Jack to end things, the Therapist offers helpful advice to try and get Aku back into form. Furthermore, Jack fervently denies his hallucination's accusations of him abandoning his purpose, Aku and the Therapist don't disagree on anything.
  • Literal Split Personality: He is Aku's more intellectual side.
  • Me's a Crowd: He's a clone of Aku that was split from the original.
  • Psycho Psychologist: As if being a therapist who is literally Made of Evil isn't enough, the fact that he's Aku having conversations with himself only makes things sound even more crazy. He's also just as Ax-Crazy as Aku's main body, as shown when he yells DIIIIIIEEEEE!
  • The Scottish Trope: Parodied, as the Therapist advises that they never speak of Jack or even call him "The Samurai", since all it does is upset them.
  • The Shrink: One that, despite being Made of Evil, is helpful and supportive of his patient.
  • Sesquipedalian Loquaciousness: He has a larger vocabulary than Aku does, demonstrated by having to explain to Aku what a "conundrum" is. Even though both of them are the same person.
  • Suddenly SHOUTING!: Mimics Aku perfectly when the original says he thought Jack would eventually DIIIIIIEEEEE!
  • Took a Level in Cynic: Decades of trying and failing to kill Samurai Jack coupled with the realisation that his magic has accidentally made Jack The Ageless and that he isn't going to go away anytime soon have caused Aku to sink into a depression. The Therapist exists to try and alleviate that depression.
  • What Happened to the Mouse?: He's never seen or mentioned after his first appearance, though it can be assumed that Aku's depression grew so strong that the Therapist lost his ability to aid Aku. Or, y'know, Aku just reintegrated him into his body.



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