Mercenary scar.

He appears to be a mature man with thin, grey hair and stubble. Contrary to popular belief, the scar on this stalker's face is not shown in the videos or in the game.

Scar is a seasoned veteran mercenary who most likely went into the Zone for his own personal gain. Scar is initially unaffiliated with any faction and works for the one that is most profitable for him. As a freelancer, his actions are tied to his employer's wallet, not his ideals.

Scar has an unusual affinity with the Zone, as he is able to survive two deadly emissions, one of which is the largest in the Zone's history.
Scar nature:
Sense of humor. Scar likes to joke, for example, about Lebedev.
Dislike of the military. Probably due to a bad experience in the past.
Integrity. Scar does not take on the first order that comes his way, even if it pays well.
Choice of tasks. The mercenary performs only those tasks that suit him.
Intelligence and education: Scar knows about such physics terms as the Mobius ring, which speaks of his high level of education.