The antonyms for the word "un-hostile" are friendly, welcoming, hospitable, kind, amiable, cordial, gentle, peaceful, and warm. These words describe an environment or a person devoid of hostility, aggression, or negativity. A friendly person is someone who greets others with warmth and kindness. A welcoming environment is one that invites people and make them feel at ease. A hospitable person is someone who is generous and caring towards others. A kind person is one who is considerate and benevolent. A cordial environment is one that is pleasant, amiable, and congenial. A peaceful atmosphere is one that is calm, tranquil, and serene. And a warm person is one who is loving and affectionate.