Ooh. So the jetpack-and-rifle angle emerge as he figures out he's got an Unbreakable situation. Some tinkerer builds increasingly glass-cannon hot-rod fighter jets that are never as maneuverable as he wants. All his miraculous close scrapes in crash landings are really a result of whatever force trapped him in this surreal choke-point holding back the forces of chaos. Once he figures out he's cursed with immortality, he doesn't care if his guns leak deadly radiation or glow white-hot, so long as they spray plasma downrange. All of it is just a means to deliver him in-person to whatever elder god is trying to swallow Earth. So he can twist its dicks off.

Which is quite a thing to imagine, from squid-faced-Khorne's perspective. You've found a thriving civilization that's barely scooting around its solar system. They couldn't even block your portal on their homeworld. Seems like easy pickings, maybe a few million scorpion-horse-locust minions killed by their measly bullets, then you get centuries of driving people mad and cracking open juicy mineral-rich planets. Your divine adversary blessed one guy. Token resistance. An admission of futility. But... your dudes keep failing. Plenty get past him, but none manage to stop him. You send the big fuckers straight for him, really nip that in the bud, and hours later he's right back up in another flimsy contraption. They can smack him to the ground and he just runs closer. You are a four-dimensional entity older than this universe. You have despoiled countless galaxies guarded by valiant forces. You were not previously aware that you could sweat.