[EDIT] I found the game: Time Diver: Eon Man, which seems to be an unreleased game :)
[url=https://en.wikipedia.org/wiki/Time_Diver:_Eon_Man]https://en.wikipedia.org/wiki/Time_Diver:_Eon_Man[/url]

Hi,

I'm struggling to remember the name of a nes game. I really want to replay it, and I hope you can help me find it.

I remember:
- the main character is a guy, medium size on the screen
- the level design is standard: walk from left to right, and some levels from top to bottom
- good graphics, I think it was towards the end of NES lifespan
- you have power-ups: shoot a vawe (semi circle shape), freeze time, and other powerups. So the game is sci-fi.
- you get the power-ups gradually, as you advance the game
- the strongest memory I have is that you can freeze time. I think the icon of the power-up was a clock.
- the bosses, when they get hit, they slowely turn pink (or maybe red). The shade of pink / red gets stronger, until they die (I think they explode)
- one of the bosses is similar to a rugby player
- the final boss it's an alien, and I think it fills the entire screen. I remember a brain, but I'm not sure.

Thank you!

Not really sure but...

This sounds to me very similar to Low G Man, with his two main weapons: an extendable spear and a special pistol, capable to freeze an enemy.

And the final boss is really a big, alien sort-of-brain huge almost like entire monitor.

Thanks for the reply, but it's not Low G Man.

StarTropics maybe?

Unfortunately no :(

Blaster Master maybe?

Based on the edit made to the post, they seemed to have found the name.