Houndoom

Houndoom is probably one of the coolest dogs that the Pokémon world has produced. Walking it certainly attracts the attention of those around you. But in battle, one should be careful not to get hit by its flames. The Pokédex entry from Scarlet warns of this:
If one is hit by the flames it shoots from its mouth, one suffers a burn wound whose pain never ceases.
Once you let your guard down, it may not just result in a scar but also lifelong pain. Even Nurse Joy and Chansey may no longer help heal the wounds.