Not suitable to your tastes or needs "the uncongenial roommates were always fighting"; "the task was uncongenial to one sensitive to rebuffs" - incompatible
Very unfavourable to life or growth "an uncongenial atmosphere"; "an uncongenial soil" - hostile, unfriendly
Used of plant stock or scions; incapable of being grafted
See also: disagreeable, incompatible, inhospitable, uncongeniality, unfriendly, unsympathetic