What are the most damaging forms of racism?

I liked the question about subtle forms of racism, but getting away from how subtle different types of racism are (and I think it’s pretty well established that it’s a hard thing to root out of ourselves even when we dearly want to do that), what forms of racism are most damaging?

You can feel free to describe who is damaged, too. Is the racist damaged? (I think so, whether he does or not.) Is society damaged, and how? (I think it’s obvious, but I’m interested in others’ opinions.)

Obviously the targets of racism are hurt by the inability to participate fully in societies and interactions they might like to join, but what are the worst forms of racism that still exist? The only forms of racism I’m familiar with are the ones I have seen or read about in North America, Europe and Australia, but don’t feel like you need to limit yourself to that discussion, either.