any idea on how to beat the lava guy in the volcanic islands?

You can't kill him. You have to shove him off all the little ledges into the water at the end, using your sledge hammers and bombs. When you run out, use the teleporters to go up levels and pick more up. They regenerate, so you have an endless supply. Try to avoid his flames and keep on killing his little helper-people. I personally found this fight incredibly infuriating and painstaking, but it IS possible, and it's the only way. I turned down the game volume and played some upbeat music to keep me going.