That someone is actively trolling games in ranked and/or normal, and they have been reported but you can see from their match history that it's an on going thing that continues to happen.
What is the best course of action? I put this player on ignore, but that doesn't prevent me from being matched w/ them again.
It's beyond frustrating, They go into games with out masteries, say they don't need them and then proceed to go lane to lane feeding the enemy team.
If it was a normal game I wouldn't care all that much because I don't expect anything but trolls/afks and people trying diff set ups/champs yada yada.