To kill the last boss you must make sure you have the following
3 aid sprays
2 blue herbs
Grenade launcher(with alot of flame rounds)
Gatling gun with lots of bullets
Just push the power boxes in the tubes and try to avoid the boss
and the huge electric gun will charge up. While it is charging
shot nemesis with all the power you got with any gun but don't get to
close to him or you will die. When the huge gun is
charged up stay out of it's way or you will be shot to death.
Repeat the same thing until he dies.
When you kill him the locked door will be unlocked; run to it and
the boss will awake again. You have a choice of running away to
finish the game or staying behind to kill him properly, but the
best is to run away and that's the end of the game.