Ambush Bug: Ambush Bug is a normal human in a ridiculous green suit amongst the gods of The DCU. In his heyday, he defeated a group of enemies with little to no effort while utterly humiliating them and could take on Superman or Supergirl before essentially defeating himself. Nowadays he's more relaxed.
Atomic Robo: Dr. Dinosaur may seem silly and incompetent, but out of all of the villains not only is he the one who survives, but he survives Jenkins. Nobody else has been able to do that yet.
The Riddler mostly got into crime just to play mind games with Batman for fun. But from Commissioner Gordon's perspective, he's a Magnificent Bastard.
The Joker is portrayed this way in some cases, too. Once he paid for doughnuts with play money with his face on it. Play money impregnated with his special formula, which was absorbed through the clerk's skin.
In general, many tend to view the Joker as just some stupid clown, only to realize very quickly why they should never lower their guard around him. He's one of the most dangerous characters in DC Comics who has upstaged the likes of Brainiac or Darkseid in terms of villainy. Lex Luther specifically never leaves Joker out of his plans because the man whose goal is to kill a god never wants to get on the Clown's bad side.
Harley Quinn, though it varies more with her. It's easy to forget that she was a brilliant psychologist, and can revert to that personality to both apply those skills to mess with her opponent's head and to pass as normal far better than the Joker can. In her most recent incarnation, it's implied the Joker actually considers her more of a successor than a sidekick/girlfriend. Harley's issue of the Joker's Asylum series explicitly lampshades this. You do not want to stop her from getting to her "puddin'" on Valentine's Day.
Captain Britain: Mad Jim Jaspers ran around an alternate universe England with a gang of ludicrous criminals, committing ludicrous crimes... and happened to be a Reality Warper of such magnitude that his entire universe had to be destroyed to prevent the Jaspers Warp from contaminating the multiverse at large. And his main universe equivalent is even more powerful... and a member of Parliament.
Deadpool: Deadpool is a madcap goofball with weaponized Your Mom jokes who thinks he's in a comic book and has conversations with his thought captions. He is also insanely good with every weapon known to man, sometimes to the Bullseye level where it's pretty much a superpower, and he has Confusion Fu going for him, as well as a Wolverine-classHealing Factor. He is an exceptionally deadly fighter and you really would rather have him on your side. Though people on his side tend want him to just shut up already even if he is the best they've got. Even Galactus could only take so much. People not on his side also want him to shut up already, not only because he's annoying but because he weaponizes annoyance: if you're paying attention to how annoying he is, you risk failing to notice the sword coming at your throat.
Several characters have commented that it's a good thing that he is a silly one, and also genuinely tries to do the right thing (although his insanity means that his definition of the right thing is probably not shared by everyone else), and will not harm innocent people or allow them to be harmed. If he had Sabretooth's or Bullseye's personality his body count would be astronomically higher and consist mostly of innocent people...
Super Goof is Goofy's superhero alter ego, complete with Flying Brick powers.
The Evronians from Paperinik New Adventures. When they don't have orders from high-caste members they're quite the goofballs. When they have orders... A Bad Future had them conquer Earth in three months, and Super Goof exists in the PKNA continuity.
Doom Patrol: The comic is populated with heroes and villains that are utterly ridiculous on paper. Reality Warper baddies who take the form of Punch and Judy puppets? A heroine who has a different power set depending on which of her personalities is fronting at the moment? Eccentric rich guy who enhances his telepathy and telekenetic ability just to impress the heroine he's crushing on? One shot villain named The Codpiece who takes Compensating for Something to extremes? Unholy Matrimony between a French gorilla with enhanced intelligence and a Brain in a Jar? And yet, the more ridiculous the hero/villain was, the more dangerous they ended up being. It's not a shock, then that this was the title that gave us the "silly only until he chooses not to be" Beast Boy, who is chronically cracking jokes, but can and will change into a cobra or dinosaur if he feels it's necessary to ruin a bad guy's day.
Empowered: Ninjette. Most of the time, she comes across as a hard-drinking, fun-loving party animal. Push her, threaten her, threaten people she cares about, or even insult someone she cares about once too often, though, and she will demonstrate that she is still a ninja, and very good at killing.
The Nome King, who is initially an incompetent Blood Knightbrute to the Adversary. Upon getting power of his own he takes Stupid Evil to new levels, and his legal system is so ridiculous that a defence attorney brags about how brilliant he is at his job because he's managed to get a relatively humane form of execution for his client (who hasn't actually had a trial, even a show-trial), but his insane slaughter of innocents is not played for laughs.
Mister Dark, the boogeyman, has Talkative Loon tendencies so pronounced it's difficult to know whether he counts as Faux Affably Evil or genuinely Affably Evil, but since he is clearly introduced as a massive threat as the god of darkness, able to take all of Fabletown on together and win, they actually serve to make him creepier.
Bufkin the flying monkey, who generally acts as comic relief with his gullibility, heavy drinking and simian interest in his own feces, but as a former captain of the flying monkeys and Fabletown's main librarian, he's a lot more dangerous than people realize when push comes to shove, as Baba Yaga and the Nome King found out the hard way.
Flycatcher, the frog prince, who wears a goofy frog hat and is on permanent janitorial duty since he keeps eating flies. Then, after suffering a Heroic BSoD, he magically Took a Level in Badass and founds an Undefeatable Little Village and defeats several powerful armies single-handedly, all while remaining a pacifist.
Foolkiller: In the limited series, Backhand, a local NY drug lord described Foolkiller as "crazier than The Punisher...He don't come off like no soldier or cop. More like being yelled at by your momma or a preacher". Admittedly, it is rather silly to lecture the person that you are about to kill, as they don't exactly live to benefit from the lesson imparted. Some of his kills occur after a brief debate in which he pokes holes in the other person's argument, then calls them a fool, hence the name.
Any tamer with a silly personality. Tamers are just monsters that look like humans with the power of the Dom, that allows them to control monsters with their voice and do a few other things... And, as shown by Zick, who has a rather silly and neurotic personality, can brainwash a flying Eldritch Abomination into hurling itself into the sun.
Leon Sinestro is a complete goofball... Who happens to have the Dom of three tamers (his own, his late father's, and another dead tamer) and wants to murder Zick and Elena for their part in his father's death.
Like every monster of his species, all sharing the species' name, Bombo is a nice and dimwitted Big Eater, most notable, in his case, for being the Plucky Comic Relief and having been sentenced to a detention oasis (the monster equivalent of jail) for being unable to fully control his appetite and being kept there long after he managed to get it under control. The scariest thing about him is that he looks like the calm form of an All-Eating Bonz, a race of monsters prone to terrifying rampages in which they eat everything and everyone in sight until they calm down, Then in the first issue of the sequel Zick, his best friend, was about to be killed by his own out-of-control Dom... And Bombo suddenly morphs similar to a rampaging Bonz and eats it. He could have done it at any moment, but he's just too nice to do it unless his friends are in danger and defenseless.
Timothy may be a tutor, the ruling species of monsters, but looks like a hairless and humorless cat and has a sarcastic and melodramatic personality (after recounting something he had done and being cheered by the monster of the Barrimore Detention Oasis he went on to recite the weather report just to prove they'd cheer him to suck up to him) and a penchant for some ridiculous plans. Being the tutor of the Barrimore Detention Oasis means it's their jailor, responsible to keep the inmates safe from the Dark Phantoms and evil monsters that live around it (the whole reason detention oasis are called like that: they're the safe spot in areas extremely dangerous for monsters, and are put there as a deterrent against break-outs), has zero compulsions about killing those threats on the spot if he can do so without risking his charges, and, being a Star Tutor, he did something awesome that earned him the greatest medal of honor a tutor could get.
Natural Tutors (the tutor subspecies Timothy belongs to) in general are this: they are all "odd" in various ways, consider a cat form an excellent disguise, and can, and will, put down on sight any Dark Phantom or out-of-control evil monster on sight. Then there's the Tutor Maxims, Natural Tutors who have been promoted to be rulers of the monsters' suspended cities and granted greater power in the process, who are just as silly as their non-promoted brethrens if not more, but have been promoted because they were just that good at what they do and could be trusted with the greater power.
New Gods: Granny Goodness is laughed at for being an old lady super-villain, until you remember that 1. She's the only minion of Darkseid who doesn't get her ass kicked on a regular basis by super-heroes/Orion and 2. She's the Goddess of Horrific Child Abuse on Apokolips, which means that whenever she is not scheming against Darkseid's enemies, she's routinely crossing the Moral Event Horizon with young girls and boys. Being a super-villain is certainly a hard job and despite her age, she is still around, so you know she's good. Also, being around Darkseid for any amount of time and not getting the Omega Beams or Omega Sanction speaks volumes as to how dangerous she truly is. Just imagine how bad her abuse has to be for it to qualify as "horrific" on Apokolips.
Plastic Man: Plastic Man is a zany, rubbery man who spouts silly jokes while having cartoonish adventures. He's also one of the most powerful members of the Justice League; even Batman, who has contingency plans to neutralize any of the League members in case they go rogue, is actively wary of him. On at least one occasion, he single-handedly took down a villain who had easily beaten Superman. When Martian Manhunter turns into Fernus, the Burning Martian, retaining his shapeshifting and Superman-level strength but losing his Kryptonite Factor, Plastic Man is Batman's contingency plan for that eventuality. In The Dark Knight Strikes Again, Batman states that Plastic Man could kill all of them, and that it would be easy. And his "Gone Rogue" plan for him is just "Pray that it doesn't happen".
PS238: Zodon is a Jerkass and the comic's bigtime Chew Toy, with most of his plans ending him up in greater trouble than he started. Problem is, this is usually because one of the teachers or the students got in his way — if they hadn't, the trouble — and much bigger amounts of it — would be someone else's.
For an early example, Zodon's idea of a prank on Captain Clarinet was crashing an airplane full of passengers, intentionally preying on his phobias of flight and failure just to make him cry, and completely uncaring about the possible civilian casualties in the process.
The Punisher: The Villains Out Shopping tendencies and angry outbursts of Rosalie Carbone (The Queenpin of an Italian mafia family in the early to mid-nineties) are often a source of comedy. However, she sends some pretty tough hitmen after the protagonists on occasion, can fight back fiercely when cornered, and maintains a strong position in a male-dominated criminal culture due to having lots of well-earning unsavory rackets and being willing to kill rival gangsters who don't take her seriously.
Secret Six: Ragdoll, no doubt. He's a master of the non sequitur, he's also perfectly capable of wrapping around you like a python and willing to snap your neck at the drop of a hat. He even gets a rant about people assuming he's just the comedy relief while attacking the rest of the team (and winning). Notably, when The Flash (2014) adapted Ragdoll, he was Played for Horror.
Spawn: The Violator. Taking the form of a pudgy clown, he's primarily around for comic relief. But at any time, the seemingly harmless clown can morph into a demonic killing machine, easily capable of kicking Spawn's ass.
Squirrel Girl: One of the most dangerous characters in the Marvel Universe is Squirrel Girl. She's a goofy, friendly, squirrel-themed hero with a notable lack of angst... and has defeated the Avengers, Deadpool, Doctor Doom, Fin Fang Foom, Galactus, Kang the Conqueror, Taskmaster, Thanos, Ultron, and Wolverine (Admittedly, she befriended Galactus instead of punching him out- which is still very impressive). Squirrel Girl plays by Silver Age rules, where the heroes always win no matter how ridiculous the situation. And even discounting her Memetic Badass nature, her powers are nothing to sneeze at; she's super strong and agile, capable of cutting through tempered glass with her claws, and can summon an army of squirrels whenever she wants.
The Sandman (1989): The queen of them all might be Delirium herself. The youngest of the Endless, she seems to be one of the least malicious members of her Anthropomorphic Personification family, but there are times where she reminds everyone that she used to be Delight, before something Very Bad happened to break her mind. And as the personification of madness, she has no trouble causing atrocities and chaos if it amuses her or even without intending to hurt someone; Blue-and-Orange Morality is in effect even more for her than her siblings.
Shazam!: In 52, Sobek at first seems like the Black Marvel family's funny pet, a silly talking alligator with a bottomless stomach. And then it turns out that he's actually Yurrd the Unknown, the Horseman of Famine, an Animalistic Abomination powerful enough to kill a Marvel.
Peter started the silly and laid-back badass hero cliche, and still does it in some instances. Spidey (in many crossover books or his own stories) is widely infamous for being a walking teenage nerd cliche with supernatural witty humor and comes off as a borderline super troll that rarely stays quiet or take situations seriously when teamed up with the majority of serious heroes. However, Peter Parker is still one of the most seasoned professional heroes, as well as one of the smartest and most competent supers in the entire Marvel collective. It's safe to say, anyone who is a big deal in the earthbound/non magical hero/anti hero/villain community knows that even if he's the snarkiest goofball around, it's not smart to get on his bad side. Even Deadpool knows this. And when he stops cracking wise...
Spider-Man has a little-remembered villain named "The Spot". And he is traditionally treated with exactly the same respect that somebody who is named that deserves — especially since his "costume" consists of a white body suit covered in black spots. But he's actually, much like the more famous Electro, a case of a villain with legitimately dangerous powers being turned into a Memetic Loser by being given a bad costume design and/or name as well as being presented as an idiot. Those spots on his body? They're not a costume choice; they're portable holes that've been welded to his skin. Long story short, the Spot is the human nexus for a Portal Network, after falling into what was basically a dimension of Extra Dimensional Shortcuts. As such, he can create free-floating arrays of portals that link anywhere he desires, and can do so whether he's existing in this dimension, or hiding inside of the interstitial space inside of the spots. This allows for many different varieties of Weaponized Teleportation, from using spots to deflect or return enemy attacks (which he can do even with the spots on his body), to his own unique version of Confusion Fu based on a combination of hiding in another dimension and attacking from random points and teleporting his opponents against their will, to closing portals when somebody is only part-way through them. The 90s cartoon series famously showed what he could do if he wasn't treated as an idiot, with him kicking Spidey's ass for most of his debut episode (luckily, he had also picked up a case of Adaptational Heroism). Then Brand New Day showed him hunting down a Russian mobster, where he was presented as Paranoia Fuel incarnate In-Universe — and he succeeded in using his powers to brutally kill his target, despite Spidey attempting to stop him. Since then, Spot has been treated with much more gravitas whenever he appears.
This is exponentially true with the Spot’s appearance in Spider-Man: Across the Spider-Verse, wherein he starts off as a goofy “Villain of the Week”, before slowly growing more and more dangerous as he learns to harness his portals to travel the multiverse, to the point where he eventually becomes a reality warpingEldritch Abomination bent on destroying everything Spider-Man holds dear.
Winslow Schott, aka the Toyman, is ostensibly one of Superman's sillier-looking rogues, but he's still a genius inventor with a wicked array of weaponry, and his robot toys can be dangerous to any innocent children who mistake them for the real thing. Not to mention the fact that his rogue android duplicate murdered Cat Grant's son in the Post-Crisis continuity.
The gap-toothed Prankster also looks and behaves funny until he tries to kill anyone with his gimmicks.
Bizzaro largely means well, and he mostly comes across as a brainless but lovable brute, but his backwards understanding of the world combined with the fact that he has all of the Man of Steel's powers means that he can unintentionally be dangerous in certain situations. The same applies to Bizarrogirl, Supergirl's own doppelganger.
Transformers: More than Meets the Eye: Brainstorm is by all appearances a typical Mad Scientist, suggesting and designing weapons of unspeakably insane intentions. Then he goes and causes stars to go out. And then there's the fact that he's secretly a Decepticon agent, and all that wacky insanity is a cover for a much darker personality.
The Scavengers are this. They're a misfit group of the worst Decepticons in existence (in the sense of not being any good at it), who show up every now and again to have a wacky misadventure usually caused by their own incompetence and bickering. Despite this, they've survived nasty encounters with the Decepticon Justice Division, Fortress Maximus, and Scorponok, and may have even saved the universe off-panel (by playing Jenga). In the final battle with the Functionists, they join the heroes and help save the day.
The Walking Dead: Negan is an eccentric, Ax-CrazyCloudcuckoolander who swears a lot, thinks of the most random things to say off the top of his head, has an over-the-top personality that confuses his own followers, and likes to speak to his baseball bat Lucille as if it were a person, mentioning how she turns him on when she strikes. However, he's also one of the most infamous villains to enter the series and is a credible badass Hero Killer.
Wonder WomanVol. 1: The Golden Age Etta Candy is a short fat girl band geek, who is always carting around a box of candy and cracking jokes. She also has a long record of fighting Nazis and evil aliens while unarmed and winning, spying for the US Government, is a decent pilot, good shot, and is nearly as good with a lasso as Diana. People underestimate her constantly, which she uses gleefully to her advantage.
X-Men: Mister Sinister is a ruthless eugenicist and solipsist who has complete molecular control over his body, making him virtually unkillable. He has subjected mutants to horrific genetic experiments, and tried to guide the creation of a superior being, made in his own image. And in recent years, he has adopted the persona of a foppish Victorian dandy almost entirely by design (one comic shows him psychically rebooting himself with a perfectly crafted persona, including an upload of five seasons of Rupauls Drag Race), so that people will think he's too effete to pull off anything serious.
