Activate Arcbound Ravager by sacrificing Optimus Prime, Hero.
When Optimus Prime, Hero dies, its second ability triggers, returning it from your graveyard to the battlefield as Optimus Prime, Autobot Leader.
Activate Arcbound Ravager by sacrificing Optimus Prime, Autobot Leader.
When Optimus Prime, Autobot Leader dies, Mikaeus triggers, returning Optimus Prime from your graveyard to the battlefield as Optimus Prime, Hero with a +1/+1 counter on it.
Resolve both Arcbound Ravager abilities from steps 1 and 3, putting two +1/+1 counters on it.