Harsher consequences for trolling in ranked and admitting to it in teamchat, please!

So I just played a game as support, spoonfed my adc, he's super fed, then 30 minutes in he decides he doesnt like our mid laner and just sits in jungle typing the rest of the game because he "wants our mid laner to lose." we were about to win but lose because he makes it 4v5. He admitted all of this repeatedly in chat. Despite our team's pleas to keep trying, he's adamant that he will not be punished for this...I feel like this is grounds for more serious punishment and there should be a way to more harshly punish this type of behavior. For me, personally, if someone has to afk for emergency reasons, its understandable, but if you are trolling on purpose in ranked AND admitting to it that should be an instaban...if the tribunal is really intended to punish behavior, this behavior should be addressed over any other kind of behavior. But as far as I know people don't really get banned...I guess I just came here to complain. It's one thing if a teammate disconnects or even rage quits, but when my teammate fully has the capacity to win the game easily for us, and they choose to sit in the jungle spamming laugh until the game ends for a reason that is completely idiotic and which they spell out in chat, in a RANKED game, it makes me wish there was an option to insta-ban someone if they pull that garbage. It was transparently bannable behavior and it shouldn't be allowed to go on for even a single game in my opinion. Thoughts? Any positive or negative reactions welcome.

Before anyone gets the wrong idea, i'd won 9 of my last 10 ranked games before that 11th game with the troll, so it's not a huge deal to me in terms of my rank. It's honestly a matter of principle.