How to really report an intentionally feeding account?

I just played with someone so toxic i had to mute them by 5 minutes. They end the game 2/12 which doesnt sound bad but when i say over the last 9 games this person has 108 deaths(12 Deaths per game average), Previous to these 9 games in their history they appear to be a normal person. All the same 9 games of tilt/trolling that results in 12 deaths per game isnt accidental. Is the only recourse the report button? I do have the summoners name but did not post for obvious reasons.