How can you report cheater if they are not the one who kill you?

Another design failure indeed. 

IDK who's the mental that thought it was a good idea to scream at potential cheaters that they were being watched just so they could turn off their cheats. I also do not understand how, in 2019, a triple A title doesn't allow you to spectate anybody but your killer (so a cheater could deal 99% of your hp but if a random finishes you off, you will not be able to spectate the cheater). The game is dying for so many reasons but cheaters (plus how non-user-friendly and annoying it is to use plus how badly designed it is) is definitly one of the main reasons.