Be careful not to confuse breeding male for alpha male. These terms seem to be neither synonymous nor mutually exclusive in Seekers of the Sun culture. Before we get to that, though, let's make sure part of his backstory is solid. The original 26 tribes of Miqo'te are well-established and rather permanent, whereas new tribes are vulnerable and almost always die out. This would be critical to his history, as surely none of the existing 26 tribes were wiped out in the Calamity.
Therefore, the cause of his self-imposed isolation would be pretty specific. More than likely, he was part of a newer tribe, whose names would start with two letters before the apostrophe instead of the usual one (since all the letters are taken up). He could also have been part of a group within the 26, but it'd be more difficult to explain the politics. Just keep that in mind, whatever he chooses.
Now, again, the leader is not necessarily the breeding male.
You're not a nunh if you don't have 20~50 ladies with you.
This leaves him a few options.
- Join a new tribe, change the pre-apostrophe letter, take on Tia, go get revenge
- Keep old tribe's pre-apostrophe letter(s), use an adjective/title as a last name to wear the isolation as armor.
- Keep old tribe's pre-apostrophe letter(s), be a Tia. Nobody asks questions, but you still don't have 50 ladies.
- Keep old tribe's pre-apostrophe letter(s), be a nunh, rebuild the tribe (doesn't leave much time or stamina for revenge)
- Become a true loner. Drop the pre-apostrophe entirely, use only a given name and an adjective/title surname.
Based on his backstory, I'm assuming options 2 and 5 will be most attractive to him. So, let's throw out examples.
Let's say his old tribe was a newer tribe (these have a hard time getting going when they break off from the main 26, so it'd explain how a single tragedy could wipe them all out). Likely, it would have been a single nunh, a few odd tia, and the 20~ women who felt like this was a worthwhile venture - maybe bigger if this was one of the rare instances the tribe picked up some momentum. We'll say their letters were... Fe and he was a Tia in that culture with the given name... Rnehalwes. He'd have been Fe'rnehalwes Tia. Then the Calamity hit and everybody died. Keeping the name Avenger as a template, he'd have ended up Fe'rnehalwes Avenger if he decided to keep the name of the fallen tribe, not join a new one, and not actually take part in rebuilding its structure. Or, he could just drop it and be Rnehalwes Avenger to show he has no tribe, he has nothing. He is just him.