Raid mode: If you quit out of a match early (whether through menus, turning off your console, or losing connection) you will receive an "early leaver" warning. If you get three of these in one day, you will be blocked from matchmaking for a ten minute period. 

Ranked: Consquences for leaving a ranked match early are more severe. You will only receive one warning before you get a matchmaking ban. The matchmaking ban for ranked lasts all day instead of just 10 minutes.