Tough one, all things I come up with are either something like posession, or deal with varying degrees of transformation along with the absorption or stealing of attributes, or "consuming" essence. Or slime girls that dissolve characters for nutrition, and only sometimes change a bit. All not exactly what is asked for.
Outright stealing some attributes, or powers like the two mentioned examples, not sure. And mostly it would be a side thing, not a whole game about it. Also what exactly should be taken, superpowers only, or mentality too? Maybe taking their form, Mystique style, as in shapeshifting?
So yeah, maybe a few more clarifications what to look for, while I try to remember something that might fit.