This is a frustrating level. Not really challenging, just frustrating. There are just enough sections with conveyor belts, spiked ceilings, and bottomless pits to drive you mad. But stick it out, and use your items to help you get around.
Returning threats in this level include the Hard Hats from Charge Man's level that ride trains, and the Crystal Joes from Crystal Man's stage. Dispose of them the same way you did before.
The second Dark Man waits at the end of the level. He's a little bit tougher than his predecessor, but still, shouldn't be too hard to take out. This Dark Man runs around the arena, a plasma shield orbiting his body. When it's extended out to both sides of his body, he's invulnerable. But he can be harmed when it's inward, away from his sides. What you do is dodge his attacks, and when he's vulnerable, nail him with the Crystal Eye. You shouldn't have too hard a time winning this one.