Mega Man 3/Wily Fortress 1

Welcome back to Skull Castle!

The first stage of Wily's zone isn't too tough, and is pretty straightforward. When you come to a watery section, use the Rush Marine. It will ease the section considerably. Thick walls that your Arm Cannon shots bounce off of can be destroyed with the Hard Knuckle.

At the end, you'll meet up with a Turtle Dispenser boss. You can't destroy the machine, so don't even try. Destroy five turtles using the Shadow Blade, and the machine will self-destruct. Be careful, though, each turtle is faster than the last.