This Proto-Tyrant was deemed a failure due to surgical complications that left its spinal cord partially exposed and its nervous system impaired, resulting in primitive behaviour and random twitching. It also suffered from an exposed vascular organ, making it vulnerable to small arms fire. The creature attacked S.T.A.R.S. member Rebecca Chambers as she explored the outer areas of Umbrella's research complex beneath Raccoon City. Rebecca was able to defeat the creature, but it regenerated its injuries and continued to stalk her through the Raccoon City Water Treatment Plant. There, it battled Rebecca and former military prisoner Billy Coen, who appeared to have killed the beast. Rebecca and Billy escaped, but the Tyrant regenerated again and made its way back to the Marshaling Yard above the Raccoon laboratory, where it confronted Albert Wesker, who finally killed it.
- Superior Strength - Although defective, the T-001 still possessed strength greater than a normal human. It would use its misshapen claws to skewer enemies.
- Regeneration - The T-virus allowed the T-001 to heal its wounds very quickly, though later Tyrant models would possess a faster healing factor.
- Heart - The T-001 suffers an exposed heart which is clearly visible upon its chest. Even small arms are capable of killing this creature, though stronger weapons such as a Magnum would still be recommended.
- Nervous system - The T-001 was prone to twitch involuntarily as it moved. Its spine was also partially exposed, which only served to provide another severe weak spot that could be easily exploited.