[Akiyoshi]

Guess the only true individual character more powerfull than him would be Yuri Ebelwin since she was so stupidly powerfull the Book of Darkness was actually a seal to contain her might and it took the entire Nanoha cast at the time of A's plus some very specific applied plebothinum to even dent her. Before that she was stompping the strongest fighters around (the Materilas i guess?) without even trying.