Game of Hot Potato, we're winning (143-107 or something - we're 7 seconds from finishing the game). Two of us go after the guy on the other team holding the bomb, and a bunny-hopping enemy starts messing with us. We're shooting at him, but not very successfully; he, on the other hand, is landing shots on BOTH of us. We throw grenades almost simultaneously (I was a tiny bit faster, I guess).
One of our teammates picks that moment to drop down from above, landing behind this guy to assassinate him. ASSASSINATE HIM!
Of course he's there long enough for our two grenades to kill him. I get the "Yoink!", my teammate gets the betrayal (because one grenade only
nearly killed him - it was the second that wiped him out). Dead guy boots betrayer - who was in a party with the fourth teammate.
We lose, 150-143, because the two of us can't get close to the bomb-holder.
I hate hate HATE that people reflexively boot a betrayer, without considering if it was intentional not.