Just because you're 7/2 doesn't mean you're not griefing
NOTE: I had the exact same post in general discussion but this is player behavior related, so here it is.
Had a Nasus in my last game (ranked). He won lane against a vayne (great!) but for the rest of the game refused to listen to pings/chat and decided to farm ALL my camps plus any empty lanes away from any action just to get to 1000 stacks. This resulted in multiple lost teamfights near enemy base because we thought Nasus was coming but he suddenly detours into enemy jungle to farm blue buff.
There really needs to be some kind of punishment for this kind of behavior. He obviously wasn't trying to win and had some other goal in mind.