The Berserk Hunter is the second boss in Doom 3: Resurrection of Evil. It guards the monorail that the Player is intending to take from the Erebus Complex to Phobos Labs. It appears after the Player uses a computer, tearing through a metal door with several fire-shooting pipes blocking the way out.
The Berserk Hunter has a large, mouthless head with four small eyes and has normal humanoid legs compared to the Hell Knight's digitigrade, goat-like legs. It is also noticeably larger than a Hell Knight, and stands a full head taller. When it uses its Berserk ability, its skin becomes darker, four bone-like claws extend from its knuckles, and its upper body and head become covered in glowing demonic runes.
The Berserker initiates the fight with its Berserk ability (denoted by a rise of flames around it) and lunging at the Player. While Berserk, it will continuously leap at the Player or slash at them with its claws. Once the Berserk power wears off, it will leap around and spit fireballs at the Player. It will do this three times before using Berserk again.
The Berserker Hunter's only weakness is its heart, which is exposed when it uses its Berserk power. The Player must destroy its heart to defeat it. A good idea would be to have the Artifact equipped before starting the fight. Immediately use it once the introduction cutscene ends and attack it with your weapon of choice. Evade it during its cooldown phase and repeat until it dies. The fleshy growth pillars in the room can be used to defend against the fireballs. The fireballs can also be dodged by strafe-running.
It is possible to beat the Berserk Hunter without the Artifact. The Player must keep their distance and side-step its leap attack and then immediately shoot its heart when it turns around. The Super Shotgun is an ideal weapon for this strategy, as the Player will have time to land a single shot before it leaps again.
After killing the Berserk Hunter, the Artifact will absorb its Berserk power. A much more powerful version of the original Doom's berserk pack item pickup or Doom 3's Berserker, all damage inflicted by the Player is greatly amplified to the point that a single punch can kill any non-boss monster, the force sending them flying off their feet.
Doom 3: Boss FAQ - posted by D00MBuggy.