I don't really see the point of the thread. I'm not intending to be thread-crappy or anything. But I really don't.
You have the width and breadth of the real world pantheons, Greyhawk's gods, the near infinity managerie of Forgotten Realms gods, immortals, primordials, devil princes and demon lords, probably other games and setting pantheons I'm not thinking of...not to mention whatever home-brewed pantheons/deities you can come up with, yourself.
If you want your party to fight Grummsh...then fight Grummsh. Go to Deities and Demigods (Legends and Lore, whatever) and pull the stats. Lower them if you feel you need to. The back of the 1e Unearthed Arcana has a complete pantheon of demi-human (and Orc) gods. Use some of them if the "big names" are "too tough."
The game is about imagination...you think D&D needs to give you MORE gods to fit your vision of what a "killable deity" ought to look like?
I do not understand.
To borrow from Nike (who is also a goddess you could probably kill and take her stuff), "Just do it!"
--SD