What is a antonym for philanthropist?

Greedy, scrooge, selfish, etc..

The opposite to a person who seeks to promote the welfare of others, esp. by the generous donation of money to good causes?

That would be someone who exploits a real or perceived problem affecting the welfare of others for their own financial benefit. Someone who works for Tobacco Control? A pharmaceutical company? A politician? The only common terms I can think of are CON-MAN and CRIMINAL.