If the last monster is killed, the battle ends instantly, ignoring all other triggers
So anything that triggers on a monster's death will usually fail.
However, if you set up a variable on turn 0 that basically tells a common event "Add this much to your AP pool", and have that variable set to 0 if anyone runs, all AP will be added properly at the end of the battle, once your common event takes place. Obviously this means that if you kill one guy and run, you'll get no AP, but that's fine since you get nothing if you run anyway. Probably the simpliest solution since you can adjust AP per battle instead of per monster.
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