Verdurous Gearhulk dies, triggering its persist ability, returning itself from your graveyard to the battlefield with a -1/-1 counter on it.
Verdurous Gearhulk enters the battlefield, putting a +1/+1 counter on itself and Corridor Monitor, and two +1/+1 counters on any other creature(s) you control.
Repeat.
Results
Infinite +1/+1 counters on all other creatures you control.