Spike Parasite

Spike Parasite enters the battlefield with
two +1/+1 counters on it.
{2}, Remove a +1/+1 counter from Spike Parasite:
Put a +!/+1 counter on target creature.
{2}, remove a +1/+1 counter from Spike Parasite:
put a -1/-1 counter on target creature, you gain
life equal to twice that creature's toughness.