Player Griefing, reported but not banned

So there was this zed, his summoner tag is <MOD EDIT>. He was given jg in ranked flex. I thought zed jg, weird but ok. He goes tp and heal and then joins me in mid. He immediatly jumps into tower, takes a turret fire and then gives them first blood. He stays between my lane and river the rest of the game taking my cs and giving them free kills. By minute 16 he had build boots of swiftness and refillable hunter pots. He wouldn't buy any damage or anything. So then at some point one of their players dove us. I put all of my abilities on the guy and then zed steals it. by one simple auto. He never spoke in chat. He didn't keep running into lane and dying. he only finished 1/5/0. I reported him but he did not get any penalty. 2 games later I see him on my team again going zed support. I dodged. I did not want another loss. How are we supposed to get a griefer like this banned??? He obviously ruined our game but he still used his abilities to deal damage. He tried to cs, even though he was taking from my lane. There are more griefers like this i see where they do not build anything correct, they feed and intentionally not play their positions and I do report them but they never get penalized!!!! I just do not understand what else I can do so they do not ruin anyone else's games. THis is a bigger issue and needs more attention.