When Arcbound Prototype dies, its modular and persist abilities trigger.
Resolve the modular trigger, putting all +1/+1 counters on Arcbound Prototype onto another artifact creature you control.
Resolve the persist trigger, returning Arcbound Prototype from your graveyard to the battlefield with one +1/+1 counter on it due to its modular ability.
Repeat.
Results
Infinite +1/+1 counters on each artifact creature you control except Arcbound Prototype.