Board Thread:General Discussion/@comment-11398218-20140521105018/@comment-1181056-20151213132101

And to add to this, the only reason Kenpachi also didn't go poof is because Gremmy specifically admitted to Kenpachi alone that his power could not defeat him. His imagination turned him into a monster that probably also affected the outcome of their fight. Since he admits defeat (even though, given the scope of his powers, he should've imagined the war being over already), he "allows" Kenpachi to live.