Reflega in Kingdom Hearts II, its more balanced in Critical mode because everything else is stronger, But it makes you invincible, while staggering the enemy and doing multiple bars of health per hit. It reflects damage taken by the barrier equal to the attacks it recieved to all enemies, but since it can be comboed it can accumulate a lot of damage before it detonates.

And it only costs 10 mp, look how little that MP bar shrinks.

Orlandu in Final Fantasy Tactics - he's basically a god compared to the rest of the cast.

Glitches with level geometry and design combined with the AI in Bethesda's games

Big bang attack from the Dragon Ball Z series games, I swear the amount of times I used that on the PSP game was just too op than most attacks.

Also the Proton Collider from C&C Red Alert 3 since it fired proton shots that splashed your base and caused heavy splash damage, if you had walls built that were anywhere close to your structures the proton shots would cause a chain reaction where the walls would explode one by one and any buildings nearby would die instantly. Compared to the Vacuum imploder (sucks units in and kills them instantly/does damage to anything within it's radius) and Psionic Decimator (immediate explosive damage with a set range), the Proton Collider was probably the most op super weapon in that game.

the Mage robes from Skyrim, that let your Mana cost became 0, this is really overpower because if you are a Ice Mage you can slow down melee foes and they will never catch you.

The Demolition Boost order in Valkyria Chronicles. It allows your shocktroopers to kill tanks. When I convince someone to play that game (which I think is fantastic and one of my favorite games), I specifically avoid telling them about how that order, because it removes all the challenge (and, I think, a lot of the tension) from the game.

And, How i Set a giff to appear down of my Reply ?.

Stealth + archery in Skyrim.  I'll never forget the first time I One-Shot a dragon.  I mean, think about that.

Vanish in WoW.  Want to induce rage?  Vanish right when your opponent thinks they've won then stun-lock them to death.

Not a perk but the .50 Anti-material rifle in New Vegas.  When you finally get one, it's pretty much over.  Same with the Buzzsaw in Far Cry

Blink in Dishonored.

Orlandu's Lightning Stab in Final Fantasy Tactics.  I usually delete him.

A fully powered Calculator in Final Fantasy Tactics can own the entire map.

CoD

EXP share for Pokemon

Makes it sooo much easier, but I'm not complaining because I like it a lot