User blog comment:Dandalore/Luffys strongest/@comment-3097081-20110205170426

In terms of a single-attack move, I'd say Gomu Gomu no Ono. Gomu Gomu no Cannon also deserves a mention, but I think Ono is the strongest one-hit move.

Gomu Gomu no Storm is the strongest multiple-hit move, and probably the strongest altogether.

These are my guesses.