I'd say more "antagonist" and less "villain".
I think Shanks is a somewhat good person, just behind questionable views and potential manipulation of Luffy. Him meeting with the Gorosei is already an extremely huge red flag, but clearly he cares for Luffy. There is definitely a more sinister mindset coming from his character though.
I'd say this is Mihawk too. He's not really a bad person, just an antagonist because he stands in the way of Zoro's final progression as a character.
this is why i think they won't be the last fights. maybe the final test before the final war? i think last few villains will be like
-kaido/big mom go down in wano
-small arc in elbaf to get more troops for the final war, reveal that usopp is a legendary hero to the giants and already has statues of himself built there, last powerups
-shanks reveals his plan to make luffy into joyboy, luffy rejects it, shanks goes yakuza mode and tries to put him down for not being thankful
-final war vs gorosei and admirals and wg allies, possible temporary alliance with blackbeard
-final battle with blackbeard for the direction of the new era
but i cant really ever predict where one piece goes