If I may suggest, just to be different from the last attempts, what if you offer a signature to start? The reason I suggest this is that each member of the legion has a signature already, that is what makes them legion material and these three are already legionnaires so they have some weight under their belts to start. Off the top of my head Matter Eater Lad could penetrate any physical defense with one bite, that seems like your special attack and that was his opening ability for his race.