Make a player-group variable and name is something, say, Playergroup1. Make another and call it something else, like playergroup2 (you will need to make one player group variable for every opposing team). At map initialization, use this trigger:
Player group- Add player to player group
...and add all the players of one side to one player group and all the players of the other side onto the other player group. Then simply make a trigger like this
Event
Player XX leaves the game with a defeat
Player XX leaves the game with a defeat
Player XX leaves the game with a defeat
(these are all players of one player group/team
Action-
Player group- pick every player in (playergroup1/2) and (defeat) picked player.
-VGsatomi