Sparkhunter Revenant

Sparkhunter Revenant can't be blocked and can only attack planewalkers.
Whenever any loyalty counters are removed from a planeswalker you don't control, put that many +1/+1 counters on this creature.
Whenever a planeswalker you don't control dies, target opponent loses life equal to the number of +1/+1 counters on this creature.