Ballistic Automaton

Ballistic Automaton enters the battlefield with three +1/+1 counters on it.
At the beginning of of your endstep, remove a +1/+1 counter from a creature you control.
{t}: remove a +1/+1 counter from Ballistic automaton to deal 3 damage to target creature.
{3}: put a +1/+1 counter on Ballistic Automaton.