Synonyms for Loner:

n.

homebody, introvert, mouse, shrinking violet, wallflower. independent (noun)
hermit, misanthrope, recluse.
introvert (noun)
wallflower.
loner (noun)
lone hand, lone wolf.
lone wolf (noun)
lone hand.
recluse (noun)
hermit, introvert, lone wolf.

Other synonyms:

homebody, recluse, shrinking violet. hermit. mouse. misanthropist
misanthrope.
shy person
introvert.
Other relevant words:
hermit, homebody, introvert, misanthrope, mouse, recluse.