Depends on the DM; essentially it's a cosmology issue.
Personally when I DM, there is no way to kill a god just by reducing its hitpoints below a certain point or making it fail a saving throw. A god is inexpliciably tied to the thing that it is an anthropomorphic personification of. As long as there is some form of conflict somewhere in the world, or will be, there is a God of War, and as long as there is a God of War, there will continue to be conflict somewhere in the world.
In my games, 'killing' a god and creating a divine job opening is a singular cosmic event. It's more than just offing another monster. You need to be able to wrap your mind around the same kind of colossal paradoxes that a god eats for breakfast before you could even considder the possibility.
You want to kill a god, then you've got to figure out how to cram a wrench in the gears of existance first. It's more complicated than just hitting ACs and overcoming Damage Reduction.