Confidence
why is there not a champion that is NOT confident in his/her ability to fight? every champion acts like they know how to fight and is confident in their abilities. you could argue that Amumu and Lulu aren't that confident, but Lulu is a nutcase that is probably thinking the League is some sort of purple squirrel paradise. and Amumu, although has amnesia and cries a lot, is still fighting with confidence.
i wish for a champion that just magically received their new found powers and are having a hard time controlling it and is still learning what is happening to them. a cowardly champion that is afraid of hurting people and themselves with some sort of massive magical power and accidentally wondered into the League of Legends....or whatever they're calling it now that the 'League' isn't canon anymore. but i digress.
now i'm not clever enough to come up with a name, lore or abilities, except that i imagine them being a girl.