Synonyms:
* Aggressive: Characterized by or resulting from aggression.
* Antagonistic: Showing or feeling active opposition or hostility.
* Unfriendly: Not friendly or pleasant.
* Adverse: Opposing or contrary; unfavorable.
* Malevolent: Having or showing a wish to do evil to others.
* Inimical: Tending to harm or obstruct; unfriendly.
* Bellicose: Warlike in nature, attitude, or appearance.
Antonyms:
* Friendly: Characterized by or showing goodwill.
* Amicable: Characterized by or showing friendliness or goodwill.
* Cordial: Warm and friendly.
* Harmonious: Marked by agreement, understanding, and the absence of conflict.
* Benevolent: Well-meaning and kindly.
* Sympathetic: Feeling or showing concern for someone or something.
* Supportive: Giving encouragement or approval.
The best synonym or antonym will depend on the specific context in which you are using the word "hostile."