The horrors of the Clone Wars permanently scarred CT-4448's mind. After the alleged betrayals by the Jedi and his brothers who disabled their brain chips, CT-4448 pledged his loyalty, heart, and soul to the Empire.
Even after clone troopers were decommissioned, 4448 continued to serve the Empire in the form of bounty hunting. His employers nicknamed him, "The Vet", for his services during the Clone Wars.
After successfully carrying out various tasks and missions for higher ranking Imperials, The Vet became one of the Empire's most trusted and reliable associates. Due to his ceaseless devotion to the Empire, 4448 didn't care about the immorality and evil nature of his bounties. In a twistedly ironic way, he was more like the Separatist battle-droids he once despised with passion; he had become programmed to complete acts of evil without question or refusal.
Similarities between The Vet and his former adversaries continued past his zombie-like commitment to wrongdoers. Constant injuries along with the accelerated aging that comes with being a clone trooper forced The Vet to use cybernetic enhancements to stay in an adequate condition. He'd had become more machine than man.