Enclave and most of the raiders in New Vegas, except the Great Khans.
I like the ending for them when they fled up north and formed a great empire, that's a nice ending for them.
I'd actually prefer it if they brought back Vipers and Jackals and expanded on them.
After all, Khans, Vipers and Jackals were the big three to originate from Vault 15.
svcks that two of them were reduced to nothing but cannon fodder.
So I think all three should be brought back at some point and to expand on the other two heavily in lore.
I don't want Enclave back, if they have an outpost in Chicago, fine, but that's it, after Fallout 4 or whatever they need to be 100% wiped out with only remnants and bunkers and facilities lost in time remaining.