Nerd in Evil's Helmet

This villain comes across as really imposing. And he probably (but not necessarily) has real power to back it up. However, he's really nerdy underneath.

He's hiding it, or trying to hide it, behind a tough façade. So it's a big surprise when he's revealed for the nerd he is. This surprise can come to other characters, the audience or both.

The classical façade to hide behind is a literal helmet. But it can be something else.

Note that being a nerd does not equal being a wimp. However, the villain might exploit such stereotypes and pull a Wounded Gazelle Gambit or similar after his nerdy side has been revealed, even if he actually is truly Badass.

See also Cool Helmet. Contrast Bitch in Sheep's Clothing. Compare and contrast Evil Is Sexy. Can be the same kind of dissonance as Villains Out Shopping.

Film

 * Dark Helmet in Spaceballs. The surprise came to the audience only, since his staff already knew him (and was used to pretending they don't know he's playing with dolls).
 * Ogre in the Revenge of the Nerds series is revealed to be this at the end of the second movie.

Literature

 * In Neil Gaiman's American Gods, the "technology kid" acts tough but other characters can see it's rehearsed and frankly, kind of pitiful.

Live Action TV

 * In Buffy the Vampire Slayer season six, the trio desperately tried to be this trope. Sometimes they pulled it off for a little while in the eyes of various characters, but never the audience.
 * Well, Warren came close, insofar as he was the only one who was actually evil, being a genuine Manipulative Bastard who Does Not Like Women and actually kills one of the hero characters whilst putting Buffy in the hospital, even though that earned him a painful death.  Unfortunately for him, he's still a Smug Snake Big Bad Wannabe, and the fact that he's a total bastard makes him far less likeable, but not much scarier.
 * Arcane, in the Dollhouse episode "The Attic".

Web Comics

 * General Tarquin in Order of the Stick. The surprise came to the readers as well as the characters. Despite being a ruthless tyrant and Chessmaster, he's also just as drama-obsessed as his do-gooder, Cloudcuckoolander son Elan.
 * Dark Smoke Puncher from The Adventures of Dr. McNinja. After seeing how his parents practically disowned his older brother for pursuing a medical degree, DSP took on a wannabe-gangsta persona to hide his intelligence and interest in robotics.
 * Krakow Brings us Kia's father. An intimidating man in a red cloak with glowing red eyes and horns. Under the hood, he's a standard businessman and Bumbling Dad with glasses, and horns.

Web Original

 * In the Global Guardians PBEM Universe, the heroes fought the schemes of a Diabolical Mastermind who called himself "Brainchild" for years before they were finally able to catch him. When he was caught, he turned out to be a disgruntled computer genius modeled after actor Eddie Deezen.

Western Animation

 * One episode of Bonkers dealt with the Collector, a Toon with a creepy mishmash appearance. He collected other toons by sealing them in plastic with a device called "the Laminator". However, when his glove was ripped off, it turned out he had five fingers instead of four, and when his mask came off afterward, he was fully outed as a geeky-looking human.
 * An episode of Garfield and Friends had the Masked Mauler, a pro wrestler so bloodthirsty that nobody will wrestle him because he never follows the scripts. When he roped Jon into a match against him, Garfield saved Jon by discovering that the Masked Mauler was allergic to cat hair, making him sneeze so hard that his mask flew off, revealing his nerdy face.
 * Dark Vegan on Johnny Test comes off as a parody of this.
 * Elmer Fudd in What's Opera Doc, wearing a magic helmet instead of his usual hunter cap.
 * Speaw and Magic Hewmet?
 * An episode of Cow and Chicken had this. The new bully in town turned out to be a wimpy kid in an inflatable suit. (Along with everyone else.)
 * Similar to the Cow and Chicken example, one episode of Johnny Bravo had Johnny accidentaly replacing the captain of a Star Trek -esque ship, where he ends up encountering and making an enemy of a hulking, menacing galactic warlord, who facially resembles Carl, and is implied to be some sort of genetic ancestor to said character. When Johnny meets him in battle on a nearby planet, the warlord removes his armor... and is revealed to be just as weak and wimpy as his earthly descendant underneath.
 * Two instances in My Life As a Teenage Robot, in "This Time With Feeling", Jenny battles a knockoff named Himcules voiced by Bruce Campbell who also happened to be a sexist Politically Incorrect Villain that grew stronger from others' pain. After beating the robot to a pulp (because she had installed a robot nerve system that was accidentally switched to feeling excruciating pain), Jenny switches to "tickle" and reduces Himcules to a "90-pound weakling" when Jenny and the town's laughter drain his power. In "Ear No Evil", Jenny (who had enormously large robotic ears installed to impress a group of Rich Bitches but only caused her intense humiliation) battles the "Lancer", a large imposing knight who steals everything in the city. After destroying his armor and weapons, Lancer is revealed to be a tiny elf-like man with ears comically larger than Jenny's.
 * Prince Zuko from Avatar: The Last Airbender. He genuinely is good-looking and a true Badass, and he's skilled at fighting, giving orders, and anything that doesn't involve casual social interaction. But sit down and have a conversation with the guy and you'll discover his Adorkable side pretty quickly.
 * Similarly, his sister Azula is a frighteningly competent Manipulative Bastard, but when she tries to act normal, she fails spectacularly.
 * Syndrome starts out as a superhero fanboy, then ascends to supervillain after being (sort of) rejected by his idol. As scary and evil as he can be, he's still a nerd in powered armor at heart.
 * The South Park episode "Make Love, Not Warcraft" has the boys fighting a Griefer who keeps killing them in World of Warcraft . He's an imposing foe in the game, but in real life...well, just take a look at this picture.

Video Games
"Vinnie: "What? I'm a collector! There's nothin' nerdy about it, I'm a collector! Lots of tough guys are into this stuff!""
 * In Max Payne 2, Max has to escort gangster boss Vinnie Gognitti, who has a bomb strapped to his head. Vinnie suggests that they head back to his place, where Max discoveres that he has a room full of merchandise from the popular Saturday Morning Cartoon, Captain Baseball-bat Boy.


 * Funnily enough, he's actually right about that.