A player did write in chat that he'll kill me with a knife irl: report is enough?

This behavior is unacceptable and a crime. You should contact the support.

Report and write the details in the discription.

contact league and contact local PD

Pretty sure someone went to jail for something similar. Theres an article i saw linked about it but i dont have the link, so youll have to google it if youre interested.

Had worse said in chat and the person continued playing ranked games without a single offensive action given to them for things that riot said are 0 tolerance and bannable offenses. The automated system is a joke, and you have to bounce around reports in player support directly to get any form of action taken otherwise the player will be given a "warning" or "chat restiction" at best for something they shouldn't even be allowed to return to the game for.

lmao......I love troll threads.

For that, you make a police report, if you think he's serious or if you think he could reasonably carry it out.

Did you tell him where you live?

If no, then you gucci, no need to worry about it. If yes, you should check yourself because only idiots would do that.