Gyarados

When this creature transforms into Gyarados it
deals 4 damage to each creature without flying.
{t}, Remove a +1/+1 counter from Gyarados:
Gyarados deals 2 damage to target creature or
Planeswalker and 2 damage to itself.
Once it appears, it goes on a rampage. It remains
enraged until it demolishes everything around it.
- Johto Pokedex.