Lokis.
My history is...complicated, to say the least. Son of Laufey, taken in after the war by the enemy, raised among them despite the fact they would never let me forgot my place, so I became determined to show them just what my place rightfully was.
Unfortunately, plans never really work out the way you intend them to, do they? Several botched attempts to conquer, including one where my manipulated legion decided it would rather destroy Asgard and everyone in it than weaken them as I planned, and I found myself destroyed in order to save a family I had denied and reincarnated into the body of a 10 year old.
That, in and of itself, lead to even more complications, both familial and otherwise, that would probably take me forever to get into, but I eventually ended up getting magically aged by a companion of mine, Billy Kaplan who you've perhaps met here, into the body that I'm in now. Because, really, you can only stay a semi-powerless kid for so long before you kind of need your full strength back.