Let's be honest, Riot doesn't care about toxic players
I don't know the formula for getting chat banned. I don't know what words or phrases will increase your likelihood. I don't swear or call other people names ever. I get called names every game and accused of inting or trolling and everything else, especially when I'm doing well for some reason.
But if Riot actually cared about people being toxic or negative or degrading or whatever, they would ban them. Not just ban the account but ban their IP and do everything they can to prevent them from being in the game. Other games and sites ban by IP, email, etc, and it's effective.
So what does that mean? Banning by user and not IP makes them money. People lose everything and start new accounts and spend money.
I started playing last year and spent money pretty frequently. Never received a chat ban.
I stopped spending money since I came back this year. No swearing. No calling people names. When people call me names like trash or wherever, I might post their KDA but j don't attack them. Chat bans.
It all comes down to banning only user names being profitable for Riot.
Toxicity doesn't matter one bit to them.