Simple trophy to obtain.
Overtime is engaged when you and your opponent(s) have no kills or the same amount and no clear winner can be declared.
I found it easiest to create a FFA match with a single opponent. Set the timer for the match to 1:00 Minute and evade/avoid your opponent until you hit 2x AP Overtime. Repeat the process of dodging and staying away until you hit 3x AP Overtime.
Hopefully neither you or your opponent register enough AP to get a kill. If they happen to kill you, even the score by killing them in return to match their score.