Attrition is an upgrade for COBRA. It allows players to either steal 2 lives from their opponent (on Assault Mode) or add 2 lives to themselves (Defend Mode) once every 15 seconds. Many of these can be a threat for opponents in Assault mode and considered an overpowered upgrade to many.
Exactly 75 Attritions (19 minutes w/ 1 COBRA or 15 seconds w/ 75 COBRAS) is needed to bring an opponent down to 1 life in Assault mode (as long your opponent does not Attrition you back or use the Support Chinook ability), or to go to full health in Defensive mode.
There is a glitch that if a player gains more than 150 lives with the Support Chinook ability and then uses Attrition, the amount of lives resets back to 150.