I love a quote I read once in a thing about alignment. "If you fix twenty neighbor's roofs, you're Jimmy the Helpful Thatcher. But if you eat the neighbor's daughter, you're Jimmy the Cannibal, and no amount of additional carpentry assistance will change that."
Yeah, the wording of OP's question is dumb for this reason. What person on this planet has done literally only evil things? A better question would be more like "What billionaire is genuinely a good person and why?" Personally the size of my list of "overall good" billionaires is a rounding error but at least the thread would be more interesting.