One of the biggest things that counter toxicity and criticism
Is being overwhelmingly positive and admit your mistakes when someone brings them up. Someone doing good? Compliment them, they'll eat that shit up and keep playing well. Someone is feeding or makes a misplay, tell them that its okay and we'll get them next time. And if someone criticizes you and your mistakes, don't make excuses, just say that you misplayed and you'll try something different next time. Im normally someone that doesnt say anything or keeps to themself but having this attitude will help your teammates get a feel for the game and keep trying.