A teammate who is absolute awful, always dead but he is so nice, saying pleasant things. You will be Iron-4 trash with him.
A teammate who is absolute best, but always demanding from you to not be trash player and do your best, not always in pleasant talk. You will be Challenger 1000LP with him.
Toxicity is a fake problem.
You are either want to win, or you want to lose.
For other purposes, normal games exist, where you can troll whatever you want.