Unlike its successors, the T-001's spinal column was exposed when the t-Virus' negative effects causing "exfoliation" of the cells immediately behind it,[excerpt 1] leaving it extremely vulnerable to small-arms fire from behind.
Furthermore, its nervous system was far more primitive than its successors, leading to the T-001's somewhat-primitive behavior; poor coordination and random twitching. These were among the reasons why it was scheduled for disposal.
Noticeable deformities and rapid decay in skin
Exposed heart and spinal column
Abnormally grown claws from single hands
Superhuman stamina, physical strenght and relentlessness