At low levels humans, orcs, and goblins. At higher levels humans, devils, demons, and aberrants.
As a rule the only "always evil" group are demons, who just want to watch the world burn. Even devils can be reasoned with and bargained with and have motivations (but watch the small print). Aberrants come close; they want to colonise and turn the world to be like wherever they came from which is inimical to the PCs.
This doesn't mean that an orc raiding party this side of the wall isn't kill-on-sight.