What's the most evil thing you've ever done?

I read the other day that we INFPs have a great capacity for empathy, but that when we're wronged, we can be one of the most dangerous types. It struck me as odd because I've never done anything truly evil or with true ill intent against someone else. But then I got to thinking that might not be the case for all of us. So what's the worst thing you've ever done to someone else?