Looking for name of older game

Some time arround 2003 to 2010, I played a side-scrolling shot´em up but for the life of me can not remember the title or find the disk.
So this will turn into a hopefully fun little adventure. I need to say that my memorys of the game are a little... wanky.

Let me get to it: Steams memory for sidescrollers is NOT GOOD for the time frame in question. I got one for 2008 and one for 2009 both of which are not what I am looking for.
The art style is simple. The heroe is grey with green accents. The camera moves with him. Each level ends with a boss fight wich is some wierd mech or millitary vehicle. One important point, there is a metric boatload of weapons. Shotgun, alien beam projectile thrower, flame ball launcher (which leaves enemies burning down to their feet), missle launchers, lightsaber. You name it!
First level ended with a leged mech, second with a helicopter (not sure). I can not remember what followed after that.

I really hope someone reads this and goes "Yea, sure! I have been playing the game named ________ all the time." I appreciate every hint like screenshots, videos, sounds (?), names, etc.

Games that are not what I am looking for:
Aztaka
Bionic Commando: Rearmed
Metal Slug series
Intrusion
Shadow Complex

It sounds like the most awesome game ever, but no idea...

But when I want to play a game like that Turrican II from circa 1992 is good 😊

NO ONE TELL HIM THE NAME JUST TEASE SHIT
Torture is fun

Is it the Metal Slug series that is being talked about here?

It was fun. Would not call it the most awesome game but it was fun.

@DeViLzzz Metal Slug looks like a nice game but is definetly not the one I am looking for.

Its not Intrusion 1 or 2 is it?

Sadly it is not.

Shadow Complex?