The Right Hand of Doom

Symmetry has often been considered a crucial element of beauty and form. So when a character designer wants to go for something bizarre, distorted, gritty or badass, they will mess with the symmetry and one of the most common forms of Fashionable Asymmetry is to make one arm much bigger than the other.

It will still be an arm with a hand and digits but it will dominate the upper body and the size may be explained by some large glove-like piece of equipment or weapon. The creators may also decide upon whether or not to have the arm's considerable weight imbalance be acknowledged with the character walking with a slight shuffle or lean.

Contrast with Red Right Hand, which, funnily enough, doesn't have to be a hand and is any mutation or defect used to denote an evil side.

Anime and Manga

 * There's Chad from Bleach, whose spirit powers manifest as a huge armoured right arm. This gets evened out with his left arm after some training with Kisuke shortly before the Hueco Mundo arc, though his second arm looks completely different, and both of them are much larger than the rest of his limbs, so it's still an example of this trope, just doublely so.
 * Neinhalt Seiger of Samurai Shodown. His weapon is a giant gauntlet with a glowing hand.
 * In Code Geass, the Guren's right arm is larger and more skeletal than its left, and a different colour to the rest of its body. It can also bombard grabbed enemies with radiation until they explode.
 * In this case, it's a Right Hand of Doom because the pilot is The Southpaw: the design of the radiation arm renders it unsuitable for any task except grabbing opponents and frying them, so it was installed on the pilot's non-dominant side.
 * The titular weapon of Busou Renkin's Homunculus Kinjou is a gauntlet on the right arm. One of its abilities is to absorb particles from the air to grow to enormous sizes.
 * Hell Teacher Nube's left hand is actually a prosthetic made from a sealed demon. When he unseals it to fight off the Monster of the Week, it turns into a monstrous claw.
 * Mobile Suit Gundam Unicorn OAV has a possible inverted example in the Banshee, which has a massive 4-digit claw dominating its left arm.
 * In Xamd Lost Memories, the titular shapeshifters have this as their most common distinguishing feature.
 * Koil Krasnov from the Ghost in The Shell manga.

Comic Books

 * Trope Namer- Hellboy with his Right Hand of Doom that also functions as his Red Right Hand. He also has a left hand of minor consequence.
 * She Hulk supporting character South Paw, who, well, has it on her left hand, actually.

Film

 * Near the end of The League of Extraordinary Gentlemen an enemy soldier drinks an overdose of Dr. Jekyll's potion and turns into a giant monster: one of his oddities is having one arm much larger than the other.
 * John Silver in Disney's Treasure Planet
 * The "Delta-6 Accelerator suit" powered armour in G.I. Joe the Rise of Cobra features a miniaturized, laser-assisted Gatling gun attached to the right arm.
 * The titular character of Finding Nemo has one of his fins being much smaller than the other. The reason why he recieved this deformity is because at the very beginning of the film, his eggshell was cracked during the battle between his father Marlin and a barracuda.

Literature

 * The Mote in Gods Eye features the Moties, an alien race with two small, dextrous arms on one side and a heavy, powerful arm on the other.

Real Life

 * Fiddler crabs.

Tabletop Games

 * Space Marines, the well uh.. Space Marines of Warhammer 40000 can be armed with power gloves and power claws. These Power Fists are basically lightsabres in finger form when it comes to enemy armour.
 * Also, Graevus of the Soul Drinkers. His right hand isn't clad in a power fist...because it's grown to about the same size as one. He has been known to use it to snap spines.
 * Eberron has the Battlefist, a magic item attached to Warforged and Renegade Mastermakers/Self-Forged.

Video Games

 * Bomberman: Act Zero, the Darker and Edgier reimaging of Bomberman, had an oversized claw glove on his lefty.
 * The Bionic Commando moved into 3D with his arm chain shot going from medium sized to overwhelming tractor piece on his left side that really shouldn't allow him to stand.
 * The Pokémon Kingler, being based on the fiddler crab, has one gigantic left claw.
 * Ragna the Bloodedge usually has a normal-looking right arm. But it transforms into a huge, black, demonic claw for his Devoured by Darkness special and his Astral Heat.
 * In Left 4 Dead 2 the Charger special infected has a ludicrously large right arm; but a stump for its left arm.
 * Similar to Kingler, the crab from Sonic the Hedgehog 2 (Metropolis zone) definitely qualifies.
 * Badass Psychos in Borderlands have one huge arm and one atrophied, useless arm.
 * Krauser's One Winged Angel form in Resident Evil 4 has a huge arm that can be used as a weapon or shield.
 * Barret in "Final Fantasy VII has a minigun for a left hand.
 * Jecht in Final Fantasy X has a massive deformed claw as the . Then in Dissidia Final Fantasy, he uses it to throw exploding punches.
 * Colonel Bahamut in Contra: Hard Corps uses a mechanical variant of these to fight you.
 * Capcom adores this trope. God Hand, Devil May Cry 4, Bionic Commando, Mega Man...
 * The League of Legends champion Riven has a relativley large right glove so she can use her BFS.

Western Animation

 * Verses the Persian (a javelin thrower) in The Twelve Tasks Of Asterix.
 * Thunder Cats villain Hammerhand.
 * Big Left Hand Guy,a lesser villain in Word Girl.
 * Transformers designs sometimes fall into this. For instance, in Transformers Cybertron, Leobreaker is capable of combining with Optimus Prime in the form of an oversized right arm. In the second live-action movie, Megatron gets an upgraded form that includes a massive cannon on his right arm (and a slightly undersized left arm for emphasis).