Magma Pummeler

This creature enters with X +1/+1 counters on it.
If damage would be dealt to this creature while it has a +1/+1 counter on it, prevent that damage and remove that many +1/+1 counters from it. When one or more counters are removed from this creature this way, it deals that much damage to any target.

Innistrad: Double Feature

Innistrad: Crimson Vow

If an amount of damage would be dealt to Magma Pummeler greater than the number of +1/+1 counters on it, all of that damage is prevented, and all of those counters are removed. In most cases, this will result in Magma Pummeler having 0 toughness, so it will be put into its owner's graveyard. Its reflexive triggered ability still triggers and it will still deal that much damage to any target.