Which character in any anime do you think has had the biggest power boost in one move (except DBZ because that's pretty damn obvious). It has to be ONE power boost. If a character absorbs some power, then 4 minutes later he absorbs some more, and then he absorbs more later on, that's not a power boost it's too constant. It has to be sudden, like Bankai. And put why.

I think either Gash from Konijiki no Gash Bell manga during the Clear Arc because Makoto Raiku decided to be a cheap **** and give him 4 new super powerful spells at once. Mayyybe Clear Note, but he was already unfairly strong before his power ups so it wouldn't count. Or Megaman Greiga Beast out. He went from a weak-ass to a godmoding psycho in 3 seconds.

Priscilla from "Claymore" well all Claymore gain a large amount of power when they unleash their yoma power and/or become awakened beings. But Priscilla enters a different league of strength when she becomes an awakened being, near unstoppable.

I havent watched too many animes where there are power boosts. I would have to say Kenpachi Zaraki when he takes his eye patch off. There are some Bankai's that are kick **** too but I am always impressed when he fights to his full power.

Son Goku from Kazuya Minekura's Saiyuki. When he takes off His diadem he loses control and awakens as the Great sage equal to Heaven. He can kill GODS at that point. In mass quantities.

Not too sure in terms of power boosts, but Naruto gets a ton, just from the power of the nine tailed fox, and he gets pretty hyped up.