Mephistomon from Digimon Tamers wanted to destroy the world for no particular reason. The closest thing to a motive we get for him is Omnimon stating he was spawned from an Apocalymon that also wanted to destroy the Earth, presumably for the same reason as the one in Adventure (if it wasn't the same one).
Bottom and Black Hole of the second and third Pretty Cure All Stars movie series. They were practically the same villains - monstrous ancient evils seeking to obtain the MacGuffin of that movie by resurrecting previous Quirky Mini Boss Squad members and giving the girls a hard time so he could take over/destroy the world. They're also powerful enough to wipe out the collective teams (knocking them back into human form in the case of Black Hole) that they HAVE to use their movie-only Super Mode to defeat them. On the other hand, Fusion, the Big Bad from the first movie and New Stage, seems to have a bit more personality, isn't seeking any sort of MacGuffin, fights the girls on his own and just wants to unite the world as a Hive Mind.
Most of the villains in Futari wa Pretty Cure were this, with almost no characterization besides being evil.
Walpurgisnacht in Puella Magi Madoka Magica, who just shows up one day to wreck the city and leaves just as suddenly; she doesn't even fight the magical girls if they don't attack her first. Her only purpose is to provide the reason for Homura's endless time loops.
The Anti-Monitor in Crisis on Infinite Earths has many of these qualities. No real personality, motivations or backstory, just ridiculous amounts of power in one package. Still, part of the concept is that he's so ridiculously powerful that it's difficult to so much as get his attention so there is some reasoning behind his Generic Doomsday Villain nature.
Doomsday, whose sole reason for being was the eponymous event in The Death of Superman. While previous Superman villains were usually really smart guys or evil robots or alien warlords or some other intelligent type to contrast Supes' Superpower Lottery, Doomsday was just raw unstoppable rage on wheels with no agenda outside destruction and couldn't be reasoned with. Most of his depth comes from the back story in later comics; Doomsday was established as a "guinea pig" that became both Nigh Invulnerable through adapting to withstand what defeated him and bloodthirsty for dying so many times to get that. In essence Doomsday is just a primitive, animalistic being - something which does not leave much space for personality.
These pop up now and then in Invincible. Unusually, they are treated by the writer with all the gravity they deserve: very little. One notable one was vanquished by all the guest stars and supporting characters in the series working together while the series protagonist, Mark, was unavailable. It was a Crisis Crossover reduced to the B-plot of one or two issues of one title.
Onslaught was more powerful than anything in X-Men history, took nearly all the Marvel heroes to beat, had no overarching plan other than "blow shit up" and existed solely to set up "Heroes Reborn", which was later retconned back anyway. Onslaught did have a back story as a psychic entity born from the combined mentality of Professor X (mutants and humans should co-exist) and Magneto (humans will never accept mutants). So he wanted to turn everyone in the world (and later the universe) into a hive mind with himself in control. However, many of the details behind his character were scattered amongst various Marvel comics titles (requiring someone to read all the comics tied into the Onslaught saga for all the details), or crammed into a book released solely as a summary for the Onslaught saga, complete with notes and information on what was planned for the saga from the writers themselves. For some, Onslaught's Generic Doomsday Villain nature made the writers' attempts to focus on Onslaught's plan changing from "kill all the humans so mutants can prosper" to "kill everyone in the world for no reason" much less dramatic that it was intended to be.
Spider Man's equivalent to Doomsday would probably be Morlun, a villain introduced by J. Michael Straczynskiduring his run. Apart from a few references to his race feeding on people who were connected to animal totems, Morlun had no real backstory to speak of, and his exact nature was never revealed. His personality was pretty bland as well, since he really only wanted to "eat" Spidey and stated that it wasn't personal. For some unfathomable reason, this was the first time a villain had ever made Spider-Man angry, even when guys like the Green Goblin and Doctor Octopus had kidnapped, murdered or otherwise threatened his loved ones. His latter appearances, especially when written by Reginald Hudlin, are driving him towards this trope as well.
The The Transformers IDW series turns the Decepticon Thunderwing into the "force of nature" variation of this trope. After he creates his "polydermal shell", the grafting process goes awry, burning out all of Thunderwing's sentience and higher brain functions, which causes him to become ultra-powerful, and go on a rampage across war-torn Cybertron, forcing both Autobots and Decepticons to temporarily ally to try and halt its advance. In the end, Thunderwing is only stopped when Cybertron swallows it whole, a process which only hastens the planet's death (which Thunderwing himself saw coming and the polydermal grafting procedure was an ill-conceived attempt to try and weather the storm it would bring, ironically turning him into the final nail in Cybertron's coffin).
Typically very common in Crisis Crossover events, as writers and artists are quicker to show how powerful their creation is than to make it interesting.
Titan from My Little Unicorn. He has all power and wants to destroy Unicornicopia just so he can spread chaos and destruction over reality, just because. His dialogue is dripping in clichés and there is nothing unique about his appearance at all. Being Stupid Evil and going with the first Saturday morning cartoon plot his minions come up with doesn't help matters.
Queen Chrysalis in the sequel.
Films — Animated
Lord Business from The LEGO Movie, who gives no motivation and has no reason for his plans to freeze the world on Taco Tuesday. Justified, as he's actually a projection of how Finn sees his obsessive LEGO-collector father.
Shinzon from Star Trek: Nemesis. His reasoning seems to consist of "Well, I'm the villain of this movie, so I guess I better mentally rape Troi and destroy Earth." The extreme actions that actually relate to his supposedly well-intentioned goals occur entirely in the opening minutes of the movie: as he was raised by the Remans, he understandably doesn't like their status as the Warrior-Slave Race of the Romulan Empire. But when he assassinates the entire Romulan Senate and installs himself as the new dictator... he's already solved all the Remans' problems. At that point his only real explanation for wanting to destroy Earth is to prove the Remans' superiority over the Romulans and show the galaxy that their Romulan empire is not to be messed with which is somewhat unclear. For a poorly explained reason (to prove to everyone that the Remans are to be taken seriously), he has a super battleship way more advanced than every ship it comes up against. He also got a planet-destroying superweapon from... somewhere.
Malekith the Accursed in Thor: The Dark World is out to destroy the universe and return everything to darkness. Why? Because light annoys him and he wishes it was gone. He's less a character and more a plot device to justify having Thor and Loki team up. Apparently they had intended to flesh out Malekith's character through additional scenes (according to Christopher Eccleston, his actor) but it was excised from the film proper.
You like the destruction they cause, but don't much care about them? Sounds like a C-list Kaiju. The better ones havesome motivation and / or are oddly sympathetic, but the ones that never appeared in more than one movie are pretty much this. Whether it's a bad trope, of course, depends on how cool the destruction is.
The original Mecha Godzilla is a justified case, it's a robot built for destruction and doesn't have a personality besides being programed to follow orders and come up with the best plan to win a fight.
The eponymous antagonist of Transformers: Revenge of The Fallen tried to harvest the sun, toppling the dynasty of Primes and starting a millennia-long war... just because. There's no explanation given in the film as to why he thinks that civil war destroying a populated solar system would be less damaging than waiting to harvest another star. Ancillary media at least tries to explain that there was an Energon shortage crippling the Cybertronian race at the time.
Rodney Casares from the Peter Clines book Ex-Heroes. He randomly turns up with the power to control the zombies, to survive the zombification with his own intelligence intact, and with enhanced physical abilities and stature he never had in life. The most that's ever explained about him is that he used to be a random gangbanger and that he was one of the first victims of the disease, but he is otherwise completely unique and exists for no reason other than to present a massive threat to the main cast.
A classic example would be Professor Moriarty of Sherlock Holmes. He's introduced in the last chapter of The Memoirs of Sherlock Holmes and is talked up to be Holmes's Arch-Enemy who is supposedly his intellectual equal, even though we never see evidence of this. He was also said to be "the Napoleon of crime", and had a hand in many of Holmes' previous capers. In this particular case, he was behind a conspiracy bigger than anything Holmes had tackled before, and it ended up supposedly costing Holmes his life. And yet he had little page time and no personality to speak of, only defined by the threat he posed. Of course, he became the Breakout Villain and has since been more fleshed out in adaptations and spin-offs.
The First Evil wants to spread evil all over the world, because it's Made of Evil and thus it likes evil. This gets bonus points for being an Informed Ability; we are told repeatedly it cannot be fought directly, and yet does damned little in the onscreen villainy department.
Earlier episodes of Buffy play with the trope quite a bit. In "The Zeppo", the generic villains are never given enough screen time to explain their motivations as that's part of the joke. In "Doomed", like most of the show's baddies, they're a metaphor for something else. Most notably, in "Becoming", Angelus decides to destroy the world just because he can, and so Spike betrays him because he doesn't see how he would gain from the end of the world.
Ditto the Beast from Angel. His status as this becomes a plot point, when they realize he's not smart enough to have come up with his plan on his own, and is serving someone else.
The Judge is an ancient demon with the power to burn the humanity out of people, which is lucky as burning the humanity out of people is pretty much all he seems interested in doing. The rest of the time he just kinda sits around, waiting to destroy the world while more interesting villains hog the spotlight.
The Weeping Angels have this as part of their character. They don't have any particular reason to torture and murder people, but they do it anyway because they can, as if invulnerable super-fast psychopaths that can hide in plain sight aren't bad enough.
Arthur Petrelli from Heroes is a conscious attempt to avert this, with him stealing Peter's Physical God powers and not using them to cause wanton destruction. Though his lack of motivation or any real plan land him into this trope anyway. He existed to steal Peter's power and as soon as he did that he faded into the background and sat around waiting for Sylar to kill him.
The Replicators. Since most of them are machines made out of Lego blocks, they have no personality whatsoever. All they do is multiply. And they just. Won't. Stay. Dead. Though this changed when the show introduced the Human Form Replicators (including the Asurans), which actually had personalities and in some cases became recurring characters. Some were even somewhat sympathetic.
Anubis, known as the most evil of all Goa'uld, his goal goes beyond wanting to rule over the galaxy. He literally wants to wipe out all life in it, using a weapon of the Ancients that sends out a wave that can do exactly that. And since he is practically the only being that would survive this, well... No reason is ever given for this (Anubis doesn't elaborate any further than stating that it's part of his "grand design"), other than that he's evil, although Daniel theorizes he may want to rebuild things in his own design (since the Ancient device Anubis planned to use was also capable of creating life... in fact, that was its original purpose).
Tokumei Sentai Go Busters has the villain of its second solo movie. Azazel is a Giant Space Flea from Nowhere with no connection to Messiah and just wants to destroy the world because... uh, because... we'll have to get back to you on that one. He basically exists to kick off a plot that isn't much about him, much like the Trope Namer exists to make The Death of Superman and Reign Of The Supermen happen. As tongue-in-cheek as the whole film was, you're probably supposed to laugh at this guy who comes out of nowhere calling himself "Azazel the Great Demon King" and trying to destroy the world because he's evil and that's what evil guys do.
Walker, Texas Ranger: The episode "Warriors," from the fifth season, sees the leader of a supremacist group create an army of genetically superior soldiers to help him overtake the law and eventually rule the world. The enforcer of the group fits the trope, as he is easily able to overcome Walker and Trivette and even gunfire by way of DNA that allows him to not be harmed by gunshots. Eventually, Walker is able to defeat this nemesis... with some help from a genetic researcher, a flask of flammable liquid and a lighted torch.
Mythology and Religion
Surtr, the fire giant who is responsible for the end of the world in Norse Mythology, is probably the Ur Example. He doesn't appear in any myths except the one that tells of Ragnarok, where he and his armies invade Asgard, he kills Freyr and engulfs the world in fire, and even that myth gives him little description or characterization. Still, while he may not appear, he is referred to in numerous other tales of both the Poetic Edda and the Prose Edda. And he's hardly the only Jotunn lacking character depth.
Between 2002-2006 in WWE, it was incredibly hard to sum up Triple H's character beyond "World Champion", "Stephanie McMahon's husband", and "sledgehammer aficionado". Oh, and "Complete Jerkass."
Prior to the Attitude/Monday Night Wars era, the "generic doomsday villain"-type storyline was used heavily in the World Wrestling Federation to build up a heel wrestler toward a world title shot against Hulk Hogan. Villains such as King Kong Bundy, Big Bossman, Akeem/One Man Gang, Earthquake and others spent would spend several weeks on TV beating up jobbers and mid-card wrestlers before their big match against Hogan ... and invariably they would all lose. note Even The Undertaker took a rare pinfall loss to Hogan in the fall of 1991, prior to winning the title. The outcomes of these matches became so predictable it was as though these fearsome bad guys were simply generic bad guys who, after screwing with Hogan, weren't so big and bad after all.
Leviathan, from the supplement Elder Evils, is a serpent made of the leftover chaos of the world. If it wakes up, the world will cease to exist. Interestingly enough, it's Chaotic Neutral, not evil - destroying the world is simply what it does. The campaign layout provided has the "good ending" condition being putting it back to sleep, not killing it, as it's literally thousands of kilometres long and hence not capable of being fought by human-sized characters. Besides, killing it might cause it to destroy the world in its death throes. And if that didn't happen, its death might still irreparably damage the balance of order and chaos and destroy the world anyhow.
The Terrasque is similar in most respects. It wakes up, wreaks everything, and goes back to sleep.
The Tyranids to an extent. They're a Horde of Alien Locusts that shows up, eats everything on a planet and uses the bio-mass to make more Tyranids to repeat the process on the next world. Certainly dangerous, certainly terrifying, but they're essentially animals. The most nuance to their backstory is the suggestion that they're attacking our galaxy because something even worse is chasing them.
The Orks fight and kill things. Why? Because... well, what else are Orks supposed to do? Fortunately their lack of motivation doesn't prevent them having personality, often functioning as the comic relief of the setting.
In general, most bosses a player comes across in game are likely to be this as they exist more as obstacles to the player than characters a in game.
The modern shooter genre has been accused of producing these frequently (usually in the form of Russia), but Solomon of Battlefield 3 probably takes the cake out of all of them. While Zakahaev and Makarov had the less-than-original motivation of restoring Russia's status as a superpower, Solomon wants to nuke Paris and New York and start World War III because... ummm... he's evil?
The Archdemon and darkspawn of Dragon Age are a rampaging force of nature, but they frame a backdrop for more complex and nuanced character conflicts, and only after confronting the antagonists native to Fereldin can the player wrap up the overarching invasion-of-evil epic. The darkspawn are partly motivated by the need to eat (often people) and reproduce, by abducting women and transforming them into broodmothers. They gain more depth in Awakening; one faction of the "Awakened" wants to awaken the rest of the Darkspawn and create a place for themselves in the world, though they are hampered by Blue and Orange Morality. Another faction follows an insane Death Seeker who resents her new sentience because it cuts her off from the song of the Old Gods.
Zemus from Final Fantasy IV wants to destroy all life on the Blue Planet. There's some handwaved justification that it's so the Lunarians can move in, but none of the other Lunarians want the humans killed to make room for them (they were "sleeping" in suspended animation waiting until the humans are advanced enough for the Lunarians to join them), so it's still pretty pointless. Zemus seems to have concluded that if the humans are all dead, it wouldn't matter if the other Lunarians liked the outcome: they'd still have no reason no to just go down to the Blue Planet. And Zemus thought he was too powerful to be in any danger of punishment.
The Shivans in Freespace seemingly exist just to be a nigh-unstoppable force for the Terran-Vasudan Alliance to repeatedly bash their heads against in a desperate attempt to defeat, with no reason yet given (and with the ultimate fate of the series, likely never will) for their actions (then again, the Shivans aren't exactly the talkative sort.)
The Unbound in late Geneforge were designed to spread a wave of equal-opportunity devastation over the world, with the expectation that the Shapers would be caught off-guard and demolished while the Rebels bunkered down and waited it out. By the last game, they're everyone's problem.
Kid Icarus: Uprising features two: The Aurum, a Horde of Alien... uh, bees that "are created from, and return to, nothing." and The Chaos Kin, a pure manifestation of evil that takes control of a host and slowly devours its soul. Both are presented as serious threats; the former requiring all the warring factions to do an Enemy Mine and team up, and the latter being a major Knight of Cerebus that causes the game to take an unexpected plunge into Darker and Edgier territory.
Several of the villains in the Kirby series, like Nightmare, Dark Matter and Zero, Drawcia, and Necrodeus are this, since they're presented as the villains for attacking Kirby's home planet with little revealed motivation or characterization to go with it.
Malladus from The Legend of Zelda: Spirit Tracks as this for similar reasons. Better design, but no personality or interesting goals and a purpose which seems to be 'Expy of Ganon to get round his death beforehand'. It doesn't help that he has almost no screen time and only one speaking line.
Ganon tends to be this depending the game, often when he hijacks the plot and thus doesn't have much time to get any characterization.
Odio in Live A Live is a reincarnating force of destruction. At any point in time there would be a hero to rise up, Odio will manifest during that time, causing terror, death, and annihilation, and directly oppose the hero. Odio will always bear a similar-sounding name that fits with that time period (such as Odi Iou for feudal Japan or Odie Oldbright for late 20th century America), making him easy to spot for the player, but the idea is that while the heroes may consistently defeat Odio, it will always rise up again in some other time. ... Except no, he isn't that at all-he's actually the mind of Fallen Hero Oersted, who has very well-defined motives. The reason he opposes the protagonists, as it turns out, is because he takes umbrage at their idealism and wants to prove a point to himself.
Justified in the case of Omega of Mega Man Zero 3. He's a Reploid simply programmed to kill and cause nothing but destruction.
Mother 3 manages to drop the "Generic" from this trope, and hard. The Big Bad of the game is Pokey Minch, now an emaciated batshit crazy Man Child who could be anywhere from 10,000 to 100,000 years old due to his abuse of the Phase Distorter. Even he doesn't really know why he wants to destroy the world, but it seems to sway all over the place between loneliness, jealousy, boredom, and insanity.
In Myth the ultimate Big Bad is the divinity called the Leveler. His modus operandi consists of, at regular intervals, take over the body of the hero who killed his last incarnation, resurrect and corrupt other heroes of ages past, and then try once again to destroy all life on the planet and rule over the dead lands. Why? It's not really explained.
The title characters of the Overlord games are meant to be classic stereotypical Evil Overlords and thinly-veiled Sauroncopycats. While the characters are often doing evil and the players do get to determine how evil they are, it's really Evil Chancellor Gnarl that carries their villain cards for the Silent Protagonists. What makes it worse is that, in the entire time you're trying to build yourself up as the incarnation of evil, you spend the entire time fighting heroes... Who are now the corrupted embodiments of various sins, so you're not even being THAT effective a bad guy. While it could be said that by defeating them you prove you are the "most evil", the Karma Meter in the game basically sways between (very!) benevolent dictator and Omnicidal Maniac. At least in the sequel, the "hideously evil" path means you have to slaughter everyone in the villages you took over while the "domination" path meant magical Mind Control.
Ballser in Something. In fact, the scenario describing the game does not even mention his name at all.
The Evil Guy in Something Else. The introduction just shows his invasion of the Bears' world and his kidnapping of the Bear Elder.
Touhoudeliberately invokes this, to justify not only each individual plot but also why Everything Is Trying to Kill You. Youkai are required to regularly antagonise and threaten humans, because otherwise youkai will cease to exist, and because it's Inherent in the System there's no real way to change it, as the newcomers to Gensokyo learn in Symposium of Post-Mysticism. Even if there is some simpler way to achieve their goals youkai will always go to "make a mess of things" as the first option (like in the Embodiment of Scarlet Devil where Remilia blocks out the sun so she can go flower-viewing during the day, even though she could have just used an umbrella), and even if some characters have reasonable goals there will always be some other troublemaker behind the scenes doing things for giggles (like Nue manipulating the Buddhists in Undefined Fantastic Object, or Seija manipulating Shinmyoumaru in Double Dealing Character).
Warcraft 3 gives us Archimonde who wants to destroy the world of Azeroth just so he can drain the powers of the World Tree for himself.
StarCraft II gives us Amon who wants to destroy everything just so that he can gain the necessary tools to clone himself. Kerrigan also came off as this in Wings of Liberty; launching a Zerg invasion to kill everyone in the sector just because she felt like it.
The GLA in Command & Conquer: Generals. While most villain factions in Command & Conquer has some fleshing out to explain their motives, even if said motives are being hungry for power, GLA's explanation, fighting back foreign imperialism, doesn't even make sense given that all they attempt to do in the story is cause destruction and don't show regard for human life in any shape or form. The fans didn't mind this much, given that China and America's characterization was almost as shallow, and the game have such a bare bones story meant the GLA's lack of characterization was more a result of how little effort was put into the story than anything else.
Goblins has Kore, a legendary Dwarven Paladin who kills anybody even vaguely connected to the "Evil" races, especially the women and children. Why? He's not saying, but his Armor Class is ridiculous enough to let him get away with it.
Homestuck's Jack Noir ends up becoming this. Starts out with a good bit of personality, but once he takes over as Big Bad he just starts wrecking things for no real reason. Word of God describes his personality as basically being buried beneath his power, and describes him as akin to a raging dragon. A later scene from Jack's perspective clarifies it further: once he's gained enough power to become the Big Bad, he's just become bored. Most of his evil acts have just been him trying to come up with something to do with his new power. It's justified, seeing that Jack's entire purpose is to be a game construct and give players of SBURB a questline to take down the Black Queen. And then his rampage across the trolls' session was out of Unstoppable Rage after Jade dies again.
The Snarl from The Order of the Stick. Not a major player in the story, but ready to obliterate everything if it ever gets loose. Though we've only heard about the Snarl in two flashbacks told by different characters with an agenda that contradict each other, and one of the main characters has admitted he probably doesn't know as much as he should about this alleged threat to the world.
"You're overpowered, you don't have a hook, and quite frankly, you're boring."
— "The Director"
Mecha Sonic from Super Mario Bros. Z. Even when he was just Metal Sonic, Eggman didn't give him a personality beyond "make Sonic dead" and "blow up anything in my way", so he's running off nothing but what he's known how to do all along.
Worm has the terrible wrath of the Endbringers, who are steadily destroying humanity for no apparent reason with regular, devastating attacks on population centers and stress points: Behemoth, Simurgh, and Leviathan.
Most members of the Masters of Evil don't have much characterization besides Zemo and Amora. Crimson Dynamo is probably the worst case, since his hatred of Iron Man is almost all there is to him.
D.A.V.E in The Batman may well be a deconstruction. He is a robot programmed by Dr. Hugo Strange with the memories and abilities of Batman's worst foes for the sole purpose of giving Batman a challenge. He proceeds to easily curbstomp Batman and steals ALL of Gotham's money just to commit the ultimate crime, but is defeated when Batman asks him to explain his origin story. Since D.A.V.E believed that he used to be a person, he basically went catatonic after realizing that he had no backstory of his own.
Doomsday basically keeps his role of catalyzing other characters' stories (despite speaking full sentences now!). He showed up for the sole purpose of starting a fight, and then getting lobotomized to show how dangerous the Justice Lords are. In the second appearance, to challenge the heroes' own morality (he's mightily destructive. He's totally unrepentant about it and pretty much told us pointblank he'll never stop. How do we stop him for good but observe our rules?) In the end he's banished to the Phantom Zone, which Batman treats as no different than a death sentence. In the sequel series he is retroactively given a back story - the same one the comic version was eventually given.
The show's version of Brimstone, a superweapon that went berserk for no identifiable reason other than to give Green Arrow a reason to join the league.
Most of the henchmen assembled in the third season, simply because there's way too many of them for them get much characterization.
In "Panic in the Sky" Lex Luthor figuratively got under Brainiac's skin (after the latter literally got under his skin) by accusing him of being one of these. Luthor pointed out that Brainiac had no real plans of doing anything with its vast store of knowledge and that it had no real reason for destroying the universe. Brainiac realized Luthor had a point and agreed to a Fusion Dance so they could actually do something with all of that power and knowledge.
Many of the one-shot villains on Megas XLR are like this. Ender, who existed to "end" things, and Gurrkek the Planet-Killer really fit the bill, however.
King Sombra from My Little Pony: Friendship Is Magic's season 3 premiere. He is built up as being a huge threat to the Crystal Empire, and is also revealed to have set up an intricate security system to prevent anypony from getting the Crystal Heart in the past, but other than that, his characterization is nonexistent, especially in comparison to the show's other villains, and there is barely any backstory for him to speak of. This isn't helped by him speaking very little and not having any meaningful interaction with the other characters.
Atomic Skull from Superman vs. the Elite has no motivation for his violence. Why is he killing people? To draw out Superman. Why does he want to fight Superman? Because it's what he does, apparently.
A few of the Sushi Pack villains fall into this, most notably the Titanium Chef, who wants to spread chaos throughout the world for no other reason than he has a book that tells him how.
Dark Kat flirted with this in SWAT Kats. He always wanted to "build a new city" over the old that would serve as a "capitol of crime", but it often seemed like he was more interested in destruction itself, as in his first appearance where he tried to nuke the city. Another applicable villain under this heading would be Volcanus, the fire demon, who never even spoke, just woke up and made a beeline for the nuclear power plant...
Trigon was easily the most powerful villain of all, seeing as how he destroyed the world approximately 12 seconds after entering our dimension. However, being the "incarnation of evil" doesn't seem to leave much room for a complex or interesting personality. Luckily, every episode with Trigon in it also had Slade around acting as The Dragon.
Most of the villains in the show seemed to be wreaking havoc just 'cuz. It doesn't help that the show had a general aversion to origin stories.
The Juggernaut in his second appearance in X-Men: Evolution. In his first, his goal was to kill Xavier for putting him in prison. The second, Xavier is nowhere to be seen, and he just decides to wreck random destruction for no reason. His main purpose in the story is really just as plot device to get the X-Men to fight out of genuine heroism despite people starting to discriminate against, even though their chances of beating him as slim.
The Light in Young Justice were heavily criticized as this before they got more characterization as the show went on, though Ocean Master who barely does anything and Klarion still never received much, even though the latter made the most appearances of the group in the first season. Similar to Justice League and Avengers above, however, the worst case of this are many of the henchmen that appear in the show who don't get to reoccurring characters, some of which don't even talk.