Played one matchmaking game, player range were 1820-1950 MMR
I was doing great mid as :fors: but after 15mins has passed 3-mates in our team were giving up and throwing game. Me and bubbless were carrying game and surviving from hard pushes of opponent team, while these 3 players wanted concede and didn't even try to teamplay or play for victory. As soon as our raxes got killed, I reached two kills away from Immortal. Then our 1-14 Nomad and his mates wanted to kickvote me, that I won't get immortal and they will Concede right after that. They kept spamming kickvotes every 3rd min, but our bubbless didn't accept. Opponent team finally managed to push down our base since those 3 players were afking at fountain. It would have been such an easy win, but kids wanted to lose on purpose and get me kicked instead of playing the game. Sad..
Report them. Not participating in a game without a good reason is considered griefing, so is avoiding the afk status (which I, from what you wrote, guess they were doing). Since you were close to immortal it seems that you had quite good chances to win the game.
I have been in similar situations. I once played a game with an arachna who didn't get mid. He flamed everyone and didn't concentrate. He ended up feeding, more or less on purpose.
I don't understand people that rage from small details and then just throw the game. If something goes wrong, afking and flaming will definitely not make anything better...