Mega Man Powered Up/Time Man

Boss: Time Man
Stun weapons: Mega Buster (charged), Thunder Beam, Proto Strike

Mega Man: Time Man will run back and forth while shooting clock hands at you, sometimes in midair. After a while, he'll use his Time Slow, slowing down your attacks and movements and deactivate it after a while. Then the cycle repeats again. It should be noted that Time Man is invulnerable to all your attacks when activating/deactivating Time Slow.

Guts Man: Despite that Guts Man is weak to Time Slow, this battle is pretty easy. You can trap Time Man using Guts Blocks. One note though: if you're playing on Hard, do not attack Time Man while Time Slow is active. This will cause him to roll and fire a clock hand, which will destroy your Guts Blocks. Unlike in Guts Man's battle, Time Slow will not hurt you, only clock hands will deal you 6 damage. But your attacks will deal 3 damage to Time Man instead of 1 (which is usual amount of damage when you fight a Robot Master your Robot Master is weak to)