[quote=@Rilla]
because they almost always end up as asspulls and bullshit. "Oh, you're beating me? One more hit and I die. care to meet my new form? it'll heal me, and make me three times stronger. oh, and much like Frieza... it isn't even my final form.'
[/quote]

Ah... the joys of BSing in Anime. Ironically, Iron has a transformation ability but it's more scene related than actual damage or willing. It had to be during moonlight though in later versions he could learn to it by will, but that didn't auto heal him and he couldn't use his weapons really. Come to think of it, if I ever use it in mid battle, I'll likely nerf it.