So...apparently there is in fact some missable achievements, like if you dont convice that specific spirit to aid you and you fight it instead, which thankfully i managed and saw the achievement pop, which means its very missable and rare. But the worst one is choosing which city to save. If you choose to save the crows one u miss out on a huge side quest that will give you said achievement and yeah...i didnt pick Minrathos....so im pretty much screwed out of it... :\ It also has 0.2% on steam so it seems like a lot of ppl missed out on it. Thats kinda dumb, why would there be an achievement just for one city but not the other?
edit: some dude on reddit who got the plat as well said, its possible to get the achievement even if I saved treviso. not sure how, but I guess ill have to see.