You can make all the bossfights in DR2 really easy by levelling up. (by starting over)
That psycho is likely the first you run into and I felt they clearly designed him to be a speedbump, the trick it to not chase him, just wait for him to come to you, dodge his attack (jump away if you don't have the dodge roll yet) and hit him once or twice. It just takes some patience. Also, the defiler (axe+sledgehammer) owns everything in the game and you can make that in the first save room. It also a good idea to bring some food.
It's pretty funny though once you're high enough level you can beat most of the psychos in like 10 seonds.