Actually, the first PVP game I played was NetTrek in 1990 — forgot about that one. We generally didn’t start calling them PVP games until 1993-ish.
I spent a lot of time on MUDs in the 90s too…. They generally had mobkill and PVP zones.
Lots of things came earlier. I’m just trying to figure out what being a “young millennial” has to do with a preference for vs computer games. We gen-x-ers were playing PVP games before young millennials were born. Atari was a staple of our childhood. Nintendo multitap was a thing in 1985.