Hellhound

Hellhounds are a monster found in Doom 3 (better known as Pinky (Doom 3)), Doom RPG (a member of the Canine class), and Doom Eternal a creature summoned by Marauders.

Doom 3
The hellhounds known as Pinkys are much more intimidating than they are dangerous. Their primary mod of attack is a bull-like charge, followed by bites and stomps. If you've got room to avoid the Pinky's charge, it's a relatively simple matter to take it out before it can lay a paw on you.

Doom RPG
The Hellhound is a monster found in Doom RPG belonging to a demonic class known as Canines. Hellhounds are brown members of the species. They can be captured with dog collars to become a trained attack dog.

Doom Eternal
The Marauder will occasionally summon an orange spectral hellhound, which chases you and delivers biting damage. While more of a nuisance than a threat, damage from the hellhound can add up quickly and distract you from the fight at hand.

Behind the scenes
The Hellhound is a monster intended to appear in Doom 64, and sadly, it didn't make it to the final cut. Its existing sculpture is that of a demonic canine with two heads, resembling the Greek mythogical Orthrus.