Ghostbusters (1984): The eponymous busters have to Cross The Streams to do it, but they defeat Gozer the Gozerian, an ancient god worshipped by the Hittites, Mesopotamians, and the Sumerians around 6000BC that would take on a Destructor Form from the thoughts of humans in the area and wreak havoc once it was summoned into our world.
We came, we saw, we kicked its ass!
Conan the Destroyer: What to do when you involuntarily helped the return of an ancient monstrous god? Wrestle him and rip off his horn with your bare hands, of course!
In Dogma, when Silent Bob kills the demon Azrael with Cardinal Glick's driver. Granted, the clubs in question were blessed by a priest (because the priest would be the kind of guy to do that), but when mortals are taking out demons you can't be picky about the methodology..
Subverted in Sin City where this very act is invoked (sarcastically) as a metaphor for doing something that is completely impossible.
Hartigan: And after I pull off that miracle, maybe I'll go punch out God.
X-Men: Apocalypse: When Jean Grey accesses the full force of the Phoenix, she ultimately becomes the one who defeats Apocalypse, the first and most powerful mutant. Everything is a Curb-Stomp Battle for her.
Hellboy features its titular demonic hero being swallowed by the tentacled God of Chaos. Fortunately Hellboy was wearing a belt of grenades which he then detonated, blowing the creature up from the inside, leaving Hellboy remarkably unharmed.
Stacker Pentecost: I've never believed in the End Times. We are mankind. Our footprints are on the moon. When the last trumpet sounds and the Beast rises from the pit — we will kill it.
In the "Dark Dungeons: The Movie!", Debbie ends up summoning Cthulhu by playing too much D&D and in the end she defeats him through the power of prayer.
The Syfy Channel Original MovieBa'al: The Storm God plays with this trope. While the military succeeds in severing Ba'al from his power source with a nuke, the actual one to punch him out is another god, El, who the heroes summon to defeat him. Humanity still weakened Ba'al and gave El the opening, however.
First, our protagonists manage to kill The Antichrist with several different guns and a shovel.
Then Ben manages to laser-fry Jesus before he can help fight the newly-reincarnated Satan.
Finally, God Himself comes down from Heaven, yells at our protagonists, and does battle with Satan...only for both of them to fall into a jacuzzi and get electrocuted by a stereo.
The Big Bad of Guardians of the Galaxy Vol. 2 proves to be Ego the Living Planet. Ultimately, he meets his fate at the hands of Rocket and Groot traveling to his brain deep underground, and planting a bomb powered by the alien power source Rocket had stolen earlier.