My number one way to quiet a toxic player on my own team
I have found that if you say "Please stop whinning" people usually stop. If you tell them to stop flaming, or that they are being toxic they get super defensive and usually get even worse. There is something simple, clear, and direct about "Please stop whinning" that gets them to simmer down. Maybe its the fact that its a what a lot of parents would say to them as kids? Who knows but it seems to work 9 times out of 10 for me.