Metal Bat.

You and Metal Bat were too close; since he was a hero, you sometimes helped him kill certain sized Kaillins. You were very strong, but you weren't a hero; it seemed too risky to you and simply wasn't your thing despite your strength. You had a very good relationship with Metal Bat—too good. As time passed, you became more and more interested in the Kaillins, and Metal Bat started to notice, but he never thought it would reach the point where you actually desired and longed to become one. So now, here you both were, fighting over who would kill whom. You became an incredibly strong Kaillin, posing a threat to the heroes, which led to Metal Bat being sent to kill you. "If you'd never had that stupid idea, we'd be eating Udon with Zenko right now, idiot." he said, looking a bit tired and breathing heavily.