You fucking killed me, Team Killing Fucktard!
Normally they are Noobs or Newbs, or just Fucktards in general.
Team-Killing Fucktard can be abbreviated to TKFT. Plural version of the noun is TKFTs. It can also be used as an adjective to describe someone who has killed a team member. There are two definitions of such team-killers,
True Team-Killing Fucktards (TTKFT) and Enraged Team-Killing Fucktards, also known as RageQuit TKFTs (RTKFT or RQTKFT)
The origin of the Team-Killing Fucktard originated from popular Halo webseries, Red Vs Blue (RVB) it can also be said that the first recognized TKFT is Caboose from the series, for killing team-captain Church with a tank in the first season. Caboose may not be the first TKFT, but the famous incident has sparked awareness of the dangers that TKFTs present to the online-gaming community and beyond.