General DiscussionYour teammate types in all chat END after a lost teamfight

Calm them down, tell them we can still win the game.

ez report

buy smoke

All chat 'ayy'

Calm them down
Motivate them
If else, press the magical button that starts with m

Just ask them to abandon so u get more gold.

Mute him and try to make the rest of the team mute him too so he doesn't have any effect on your teams performance.
Also you could explain him that his behavior is probably losing him a shitload of mmr points.

make him type "let us end*"