I'd say the most powerful character in all the anime and manga is Goku from Dragon Ball he defeated the ultimate and final form of buu, a buu who destroyed the earth with one shot, a being feared by everything in the universe, know i'd say that's a pretty damn good feat. Also, Lain and others will have no effect on Goku, because he's stronger than a God, take the Supreme Kai for example he's the god of their universe and his power doesn't even touch Goku's. Lastly I want to state that in the end of GT, Goku fuses with the Dragon Balls taking him up to a higher level than he was ever before. So I'd say Goku hands down.