Version: One
Gods Eliminated: Nil
It is known that you can’t kill a god in combat, no matter how powerful your weapon. They are immortal, immune to all harm. Fair enough.
But a god is predicated on belief. Erase the knowledge of, belief in, reverence of, fear of, a deity and they are nothing. Sand in the wind.
Killing small gods, then, is easy. One might feasibly slaughter their followers; convince those that have simply heard of them that it was but myth (the supernatural never quite escapes a kernel of doubt, in any case); and burn up all written reference to them.
Killing an elder, established god is a much trickier matter. The volume of material mentioning them a veritable torrent, their followers legion. More than the work of one person, even over a lifetime dedicated to a cause unmaking.
To kill a god, ironically enough, you need to build a religion. One dedicated to their nonexistence. You must perpetrate the belief not only that the diety in question does not exist, but has never existed and could not exist. You must inspire this belief to be so fervent and infectious that all reference to them is blotted out, pages from tomes torn and burned, memories purpousfully cauterised.
Do not stray into inspiring hate. You are preaching absence, indifference, forgetting.
Finally and most precariously, you must cause your very followers to disband from your cause, engineer your religion cannibalising itself into a nonexistence that leaves only the absence of its once-divine intended target behind in its implosion. This absence will be invisible by definition, an unseen scar in the fabric of reality.
Belief is the most powerful thing. Its absence evermore so.