apathetic — If you describe someone as apathetic, you are criticizing them because they do not seem to be interested in or enthusiastic about doing anything.
disinterested — unbiased by personal interest or advantage; not influenced by selfish motives: a disinterested decision by the referee.
dispassionate — free from or unaffected by passion; devoid of personal feeling or bias; impartial; calm: a dispassionate critic.
unconcerned — not involved or interested; disinterested.
unenthusiastic — full of or characterized by enthusiasm; ardent: He seems very enthusiastic about his role in the play.
calm — A calm person does not show or feel any worry, anger, or excitement.
peaceful — characterized by peace; free from war, strife, commotion, violence, or disorder: a peaceful reign; a peaceful demonstration.