@krinid: You mean like a shared one? Or are you just asking about the block list functionality? (https://www.warzone.com/wiki/Block_list
) Warzone lets you block people but it doesn't really do anything meaningful unless they're actively stalking your or something. Doesn't work/hasn't worked as a mechanism to avoid toxic players.
It's one thing if your opponent asks you to surrender and you think you have a shot. But if you're actually losing and you keep playing just to annoy your opponent or out of a sense of wounded honor, wasting your own time as much as theirs, then you must be a child.