There are many reasons why people would troll in a ranked, they are usually Yasuo, Vayne, Yone or Lee Sin mains who had a bad day (or a normal day in many cases) and someone stole a minion from them, then, they will just directly troll or refuse to help until they get their power spike, in everyone’s case but Lee Sin that spike would be at 0/10/1. Those who think they are Gosu and always goes 0/25 are the best players in the world, in their mind, of course, but, what makes this players troll?
All those champions have something similar, they require skill but have a lot of damage, also, they are squishy, it means they will die against everything if they miss play, which is probably that happen, often, they’ll just get mad at themselves and then starting to play even worse on purpose, because “no team” or “jungle diff” when they went in against 10 enemy minions. They want to feel that they are faker and that they can do the same in the same way, just going 1 v 5 and taking a pentakill, but in reality, that doesn’t happen, because those xXxUchiha_Slayer69xXx will not carry and not do enough damage, they can get their 0/10 spike, yes, but they can’t manage to have a game long enough to recover. They know it and that’s why they directly decide to troll, so they avoid accepting the fact that they are losing by themselves instead of losing by others, because it’s always someone else fault.
Let’s not talk about the flame and how they start blaming jungler at minute 3 for no reason, or top for not TP or mid for not roam. They will blame everyone who can be blamed, because there’s no shame on thinking how good they are. For those players the solutions is buying elo boost, not them, well, also them. But not exactly for them, for you, mostly, so when you cross one of those, the booster will simply carry, depending on if you are playing with him or not, of course, you can choose between solo or duo boost, depending on your time and your availability, or simply your desires.
Those players will never disappear, we need to avoid them or hard carry them, and always mute them. Because they will be flaming in a non-stop way every single time they can. They troll because they think they are better than they actually are, this also can be known a dunning-krueger.