If you want to go really ick on death attacks, how about not taking certain bacteria/viruses; the human immune system kills invaders, but what if it can’t?
Stat-wise, you can stick whatever numbers balance for your group, but describe it in terms of disease.
To shift the fight away from simple slug-fest, you could even have the power go off as the players arrive, washing over them with no immediate effect but dooming them to nigh-incurable sickness in the mid- to long-term, then have your god offer to reverse it if they submit. That way the players have a choice between potentially winning but having to cure themselves or abandoning their fight; after all, the replacement god might not be able to just reverse it, or might decide it’s a good thing if mortals who have turned godslayer don’t survive and claim they can’t.
To hit them in the BITs even harder, is there a way you can make one player want to do hardcore stabby Death to Death Itself! and the other have reasons to negotiate? Any terminally ill children or beloved ageing relatives? What about the best magician/warrior/&c. returned from death to tutor them?