Seven-game losing streak after a five-game winning streak.
Give me such amazing things as Jax/Soraka ADC seven times in a row and make them refuse to forfeit and say "It's just a game! Have fun" like it excuses them ruining mine.
Give me such amazingly toxic teammates that I have to report two to five of them per match, but only in these loss-streaks! Very rarely otherwise. Wonder why. Must be the fairies.
But hey, it's a balanced 50% winrate, right? Totally not extremely toxic, frustrating and unfair, right? Totally makes that "player agency" a thing when our team'd lose to theirs even if we hired Faker to carry.
[slayer-jinx-unamused] [zombie-nunu-bummed]
The MMR system has a natural side-effect: people who win too much will start to lose when they reach into an MMR full of people on both teams that're so far above them because they eventually contribute so little of something to their team that they "force" a loss.
In the above, someone reaches their true MMR when they win and lose 50% of the time not because of allies that carry or teammates that feed, but because they contribute as much to the game as literally everyone else there. And that is also where you learn to improve, too, because you have to learn new tactics.
Forcing people to lose due to teammates objectively worse than theirs (or you, or both!) is NOT how you remedy someone winning so many games in a row, and in the end just promotes a feeling of helplessness and spite that contributes to the toxic atmosphere.
