Fishbone D is a strong villain that fought with Ichigo. He was so powerful that Ichigo was nearly defeated and the world would have been destroyed. Add to this that Fishbone D may have only been using 10% of his power and we have a dangerous villain on our hands. Fishbone D is the strongest being in existence and has shown this many times over.

His Main Form

His Record

W Kirk
L Ichigo
W Longshot