Dekar in Lufia 2. Dude gets a unique weapon that no other party member can use, with a unique skill that deals 50% of an enemy's current HP.

It can't miss, it proccs 100% of the time, all you need to use it is to fill up your IP gauge which is completely trivial. This attack also works on bosses, which means Dekar is capable of hitting for several thousands HP worth of damage in a game where your best fighters will at cap out in the high hundreds per hit.