My characters come from many different sources, and one of the inspirations for Ruby was Peter Rasputin, a.k.a. Colossus of the X-Men. Often seen as one of the dullest characters in the franchise, I found Peter anything but, carrying a sensitivity and gentleness uniquely his own that belied his power. The Marvel Universe was fortunate for this, because Peter's size and strength would've made him an incredibly destructive force if he were even slightly less restrained. We saw glimpses of this in the rare occasions when Peter was pushed too far, such as when he broke a villain's neck with a mere flick of the wrist during the Mutant Massacre. (Of course, said villain had participated in said Mutant MASSACRE, so it's impossible to feel sorry for him).
Ruby shares this "gentle giant" nature with Colossus, especially the part that comes when someone is actually horrible enough to get on their bad side.
I actually agree with you on Colussus, he is incredibly underrated.