The following is the recommended order in which to destroy the bosses in Mega Man 5:
BOSS - WEAPON Star Man - Use Mega Buster (also weak to the Water Wave) Gravity Man - Use Star Crash Gyro Man - Use Gravity Hold Crystal Man - Use Gyro Attack Napalm Man - Use Crystal Eye Stone Man - Use Napalm Bomb Charge Man - Use Power Stone Wave Man - Use Charge Kick
In Proto Man's castle, there are 4 Dark Men of different color. Use the following recommended weapons:
BOSS - WEAPON Dark Man 1 (green) - Use Water Wave Dark Man 2 (silver) - Use Crystal Eye Dark Man 3 (purple) - Use Gyro Attack Last Dark Man (red) - Use Beat
You'll finally be in Dr. Wily's Castle. Use the following recommended weapons:
BOSS - WEAPON Spiked Worm - Use Mega Buster and Crystal Eye* Angry Circle - Use Gyro Attack Wily Giant UFO - Use Mega Buster Wily Machine - Use Super Arrow Wily Capsule - Use Beat *For the Spiked Worm, the player must use the Mega Buster on the sections of his body to jump on them and, when Mega Man gets to hit the head, the player must use the Crystal Eye to damage it.