Japanese UKpostsr セルジオ put out a video of them beating this mission with only 200 HP, but that strategy mostly involved kiting the boss around on a bike, and I wanted to find a way to beat the boss on my own two feet. After several days of experimenting, I found a way, not only to beat it without a bike, but without any support equipment at all, and while this was supposed to be a 200 HP run, I actually ended up beating it without getting hit.
The secret to this fight is that the Nameless (God) has the same flaw that Cosmonaut AI does, it can lose sight of you. By finding something to hide behind, you can make the Nameless stand still, and when it does you can approach it from behind to set a C70 Bomb ambush right under its feet. Using this strategy, this mission really only has one major problem. The cosmonaut spawns.
While I don't know exactly how much health the Nameless has, this strategy heavily relies on knowing when the cosmonauts of Phase 1 and 2 are going to spawn, so after a lot of trial and error this is the end result. Whenever I think the Cosmonauts are about to spawn I try to place my C70's in a circle around the Nameless, which usually works but I got a bit unlucky in this case and a Cosmo survived in Phase 2. After the Cosmonauts in Phase 2 are killed, Storm 3 and 4 show up and keep the Nameless distracted while you get to snipe from a distance. If you are far enough away, the Cosmonauts of Phase 3 won't focus on you, and you will be outside the range of the meteor attack. I do have one extremely close call with two meteors (which I don't even know how I survived), but aside from that Phase 3 is a cinch.