Board Thread:Lore Discussion/@comment-4705438-20140201121316/@comment-27007772-20141027154849

None of the above. The strongest thing in all of TES is Numinduim with no contest. He has the ability to erase entire races with the flick of a finger, and doesn't risk waking the godhead because of his origin being neither of their branches.

The second, is Alduin, because he ends the Kalpic cycle, and has killed EACH of those deities countless times, excluding maybe Talos, who may be new to the Kalpic cycle.