I always see a lot of posts here about the reporting system not working or not doing much. I am not sure to what extent the system actually works, but there's a pretty easy way to ensure you'll get someone punished. Whether you encountered an extremely toxic player or a griefer, as you long as you can get screen shots or video footage of that player you're set. All you have to do is go to Riot's Support site, select Valorant, scroll down and press "Submit a ticket" (make sure you're logged in). Choose a request type of "Report a player", explain what was the situation and add evidence of video footage or screen shots. An employee should respond in a few days at most and will review the case, they might request you to add some additional info and you should be set. I have done it before and i know that actions were taken towards the player i reported. If the player you reported wasn't reported much before then maybe they won't be punished but it will make sure that in the future they might.

May the MM gods bless you with good teammates :)