I am betting this river, he isn't checking a set on this river and there aren't many hands that play this way that you don't beat.

AT, A6, T6 are the only real hands I see him on here.

You have an A so there are only 12 (A6 and T6) but there are 9(T6 that you now beat). His hand range is probably slightly higher than this. But if this is his hand range the pot is big enough to allow a call even when you are ahead of less than you are behind.

He may have tried getting cute with A5, 65, T5, but that sucks.

Bet/call vs this opponent. On second thought Bet/fold.

I don't think you get c/r here ever by a worse hand actually. Bet/Fold probably makes sense.