I knew I'd get Lord DGAF.
In a game state that actively allows this level of tilt, unfair mechanics and Riots' laissez-faire attitude on player reaction (It's normal for the game to be frustrating 50% of the time!)
I find apathy is really the only answer. At some arbitrary point in the game where my Silver 2 brain decides the game is lost without hesitation: /muteall, open up a YouTube video on the other monitor and devote 70% of my attention to that and the only the minimum 30% of brain function neccessary to make it not look like I'm completely trolling in the League game. Single Player mode engaged.
Stop taking the risky initiative that is necessary to possibly turn around and play overly defensively, virtually guaranteeing a slower more arduous defeat, farm every lane as far up as possible while being safe and then mindlessly move around the safe area map when there's no safe gold to take, play chime collecting simulator if I'm on Bard to transform League from frustrating MOBA to a serene casual racing sim as the enemy team leads me on a 700 movement speed Benny Hill inspired chase through their jungle.
And hilariously enough, as per Riots' own Terms of Service this is the "correct" way to manage tilt. All of the other personality types risk venting in chat and earning a ban for their trouble. When by definition they are still trying to win and are a bigger asset while tilted then someone like me, but are just more passionate. That's not the only reason being DGAF is de wae
Barbarians are too emotionally invested in the game, Paladins chasing an arbitrary win condition to enjoy themselves that is only guaranteed in 50% of games and the Scarred Veterans allow the toxicity of League to slowly pool into their soul, maintaining virtually no barrier between them and this cesspool of a game.
It is the DGAFs' of the world that play League of Legends. Everyone else lets League play them.