Guts Man is a Robot Master created by Dr. Light, but reprogrammed by Dr. Wily. He was first seen in Mega Man as one of the games 6 Robot Masters. Initially, Guts Man was built in order to help with construction on buildings. According to multiple sources, he was made by both Dr. Light and Dr. Wily, though more commonly just the former. Apparently Dr. Wily ended up corrupting Guts Man and turned him into a villain along with various other Robot Masters. Mega Man was then required to go through his lair and then defeat him, preferably by using the Hyper Bomb.
To defeat Guts Man, shoot him from a distance. Look out when he lands after he jumps, because he can make the whole ground shake like an earthquake! Whenever Mega Man gets caught on the ground-shaking, he will get stunned with him falling on his behind. So, before Guts Man lands, jump & you will escape the ground shake. Use the high grounds to evade the blocks that Guts Man throws at you or wait for the blocks to hit the ground then jump over its shatterd pieces. Guts Man moves by jumping. You can run under him when he jump towards you, then jump as he lands on the ground to evade the earthquake. The Mega Buster can deal 2 points of damage to Guts Man.
Guts Man is weak against Hyper Bomb, which you will get when you defeat Bomb Man beforehand. It takes three bombs to defeat Guts Man. The bombs don't go off after it was thrown, so time your bomb-thowing carefully.
In Dr. Wily Stage 4, you will encounter him for a rematch. Use either strategies at the best situation.