坑队友 (kēngduìyǒu): to throw / drag down teammates

Classic gaming/sports complaint. 坑 (kēng, 'pit/trap') as a verb means 'screw over / set up to fall'. 坑队友 = 'pit your teammates', i.e. cause them to lose. Universal across MOBAs, FPS, and ranked play. Often combined with 菜 (cài, 'noobish'): 又菜又坑 (yòu cài yòu kēng, 'bad AND throws').

culture

A core grievance in Honor of Kings (王者荣耀) and LoL ranked culture, where solo-queue means random teammates can torpedo your rank. The opposite is 带飞 (dàifēi, 'carry to victory') — a strong teammate carrying weaker ones up the ladder.