the.com/lone wolf

means A person who prefers to work, live, or act independently rather than as part of a group.

from A 19th-century figurative extension of the literal animal description — wolves occasionally observed living or hunting apart from the pack were called 'lone wolves,' and by the late 1800s the phrase had leapt into English to describe solitary, self-reliant (or antisocial) humans, especially criminals and loners in popular fiction. The irony, as the essence notes, is that real wolves are deeply social pack animals, so the metaphor borrows the rare exception to describe the human rule.