Player told me to kill myself.

If the player said this in-game, as you mentioned, you should use the post-game report feature to report this player. Escalating reports to the Player Behavior team directly should occur as a last resort, such as when you're being harassed out of game, don't have access to the post-game report function, etc. In this way, the Instant Feedback system is able to gather behavioral data on players to limit their toxicity and subsequently reform them.

report at end of game for negative attitude

Please describe the process step by step for me? https://gfycat.com/EthicalEmbellishedDragonfly

Report them, capture a screenshot, and send in a support ticket.

People are so obnoxious over the internet. Vomit.