Some of the angriest song's I've ever seen were written by Eric Bogle; "Honest working man" comes foremost to mind. Some of Leon Rosselson's political songs are pretty angry.

I judge an 'angry' song by the feeling I have while singing it. Some anti-war songs, for example, I find are very provocative and sad, and perhaps make me feel angry as a subject in general, but not necessarily while I'm singing them. And then again, the feeling of the song invariably changes, depending on what mood I'm in, what political and social events are presently in the news, etc. For example, while participating in anti-Gulf War demonstrations, I felt a lot of anger while singing anti-war songs. I probably wouldn't feel that way about them right now, however.