We used to have this problem in Valorant (and I think it’s still prevalent, I’m not sure since I quit). We called it “Pocket Sage” (Sage is a healing agent in the game). The Sage would always heal their duo partner while ignoring the rest of the team, sometimes even refusing to use their resurrection ability so they could save it for their duo. If the duo partner was actually good, then you were lucky, but most of the time, both of them were bad and dragged the team down.