hardened
adj.adj. describing someone who has seen or done something so much that they are no longer easily shocked or upset by it.
adj. having become habituated to a particular environment or experience, typically one that is harsh or difficult, resulting in a lack of sensitivity. Often used to describe individuals with extensive experience in crime, war, or high-pressure professions.
The hardened detective didn't react to the messy crime scene.
After years of working in the emergency room, she had become hardened to the sight of serious injuries.
Even the most hardened political analysts were surprised by the sudden shift in public opinion following the debate.
Typically used attributively before a noun like 'criminal', 'soldier', or 'cynic', but can also appear predicatively after 'become'.