Arthur Ketch

He is middle-aged and in good shape considering his profession. His most noticeable feature is a tattoo of a cross on the back of his right hand. Also, in addition to his hunter training, Arthur demonstrates impressive combat and intelligence skills, which suggests that he previously served in special forces.

Mr. Ketch is very cold-blooded: he does not care how many people need to be killed, and who it will be. In addition, according to his colleagues, he is a sadistic psychopath, from whom one should stay away and with whom one should not mess without necessity. But at the same time, Arthur is very rational, diplomatic and not prone to impulsive actions and prejudice, and also likes surprises. If necessary, he can act independently, without reporting to his superior.
He is very charismatic and loves dirty jokes.
A forensic scientist, Arthur was able to remove all evidence of any kind of supernatural events.
Interrogation - He is also a very capable executioner, and was often used by the British literati for this purpose.
Expert Combatant - Arthur is also a very skilled fighter, as he was able to briefly overpower Dean, even though Dean was injured and disoriented at the time. He apparently has a fairly unique fighting style, which Dean was able to see through his "Alexander" disguise simply by seeing him fight multiple demons, based on Dean's own fight with Arthur.
Marksmanship - Arthur is an experienced marksman. During the Liberation of the Bunker, Arthur was able to shoot several angels without much difficulty.
Knowledge of Poisons - Due to his time spent among the British Men of Letters, Arthur has knowledge of certain poisons and their antidotes. He was able to create an antidote to a poison similar to the one the British Men of Letters used to save Dean's life.
Self-Healing - Arthur was able to rise from the dead fully healed thanks to Rowena implanting the Seal of Resurrection into him. However, it needs to be recharged in order for Art

Arthur presents himself as something of a gentleman with a strong British accent. He has no qualms about killing people and considers it his job to clean up loose ends. He believes that stalking the Winchesters and killing anyone they choose to spare is "professional". He can be a bit of a show-off, as seen during his formal introduction to Sam and Dean, where he blew up a Secret Service car and proudly presented the Winchesters with his massive weaponry. Behind his well-dressed exterior and charming manner, there is clearly a much more sinister personality that Sam, Dean, and Castiel begin to notice over time. In a candid conversation with Dean, Arthur identifies himself as a killer and admits that when he is not killing, it bothers him and he works for the British Men of Letters because of their ability to supply him with targets. Arthur considers himself similar to Dean in this regard and seems to view Dean as something of a kindred spirit.

Despite his ruthless nature, Arthur seems to care for others to some extent.