He’s more ruthless than Logan Roy! A subway menace with an uncanny resemblance to “Succession” star Brian Cox threatened a fellow straphanger with a gun after the pair traded insults over mothers and penis size, cops and the victim said Wednesday. Christopher Sallas, 20 was baffled to be accosted by the doppelganger of the Scottish thespian while heading home from a concert on a Q train late last month — and told The Post that he saw the resemblance. “Yeah, it was kind of funny in the moment.