These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Crash Man can also be considered this. He is pretty much the character who can dish out the most damage in a large area with a single shot. The only drawback is that he can't fire straightforward when jumping, and he can't fire rapidly. To put it simply, his weapon does these:
If you know how to use him, Flash Man can be an extreme Game Breaker. For instance, Shadow Man can be very hard and annoying to dodge, but if he allows Flash Man to use the Time Stopper, he can basically damage Shadow Man enough to where a lot of his health will be taken away.
That One Boss: Bubbleman and Flashman, again. Or any boss on anything harder than Easy Mode.
Zero-Effort Boss: The Guts Tank. Hide up against the blast shield and just keep summoning boulders. They'll break hitting the shield and splinter out, and some will hit the Guts Tank. Meanwhile, the shield will protect you from all harm.