Can someone tell me which cleric has the most powerful necromancy spells BUT is still a good allighnment (which ethos)

I assume Illmater (if you can have them) but that is just a guess, as they do the whole suffering thing, and I think healing is necromancy too.

Wail of the Banshee and Horrid Wilting are the highest 9th level Necromantic spell that clerics can cast. Wail of the Banshee is a Domain spell that is available only to clerics of Oghma and Talos. Horrid Wilting is a Domain spell for cleric of Ilmater or Talos. So based on that, Ilmater is probably the right answer, since Talos worshippers have to be CN, CE or NE. However, Talos is a BETTER choice is ethos is NOT a restriction.