Such troll is not allowed to play to ruin matches

I first met this troll feeder in one of my match. I was {{champion:9}} Jungler. While this troll playing as support{{champion:99}} with her{{champion:523}} adc . This troll purposely feeding entire match since 2 minutes into the game. Kept feeding by standing still and let enemy team to kill her and made their ADC fed out of control while spamming annoying chats to trigger my entire team. Even opposing team agree on reporting this troll with a score of 0/19. Few hours later, this same troll ruined another match on other players with the same troll feeding tactic with a score of 1/10. How can such players be allow to roam freely??
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