Modifiers matching loner:

• introverted,
• fast,
• immature,
• driven,
• lonely,
• clumsy,
• reclusive,
• predatory,
• buffoonish,
• independent,
• cunning,
• dangerous,
• agile,
• violent,
• petty,
• laconic,
• bohemian,
• creative,
• strong,
• romantic,
• out-of-touch,
• inventive,
• aloof,
• well-meaning,
• delusional,
• friendly,
• animalistic,
• socially-unintelligent,
• formidable,
• taciturn,
• shy,
• endearing,
• brutal,
• affable,
• dispassionate,
• resourceful,
• juvenile,
• literary,
• bald,
• honorable,
• anti-social,
• moody,
• ruthless,
• childish,
• uneducated,
• stoic,
• protective,
• straightforward,
• isolated,
• obsessive,
• mumbling,
• unintelligible,
• schizophrenic,
• detached,
• depressive,
• defiant,

Simple categories matching socially-unintelligent:

• invalid,
• person,
• loner,