There are many words that can be used as synonyms for "hostile to." Some of the most common include antagonistic, unfriendly, against, opposing, and opposed to. Others include adversarial, combative, confrontational, hostile, and inhospitable. These terms all suggest a negative attitude toward someone or something, indicating a lack of cooperation or support. Depending on the context, other synonyms may be more appropriate, such as opposed, averse, or resistant. Overall, it's important to choose words that accurately convey the intended meaning and tone, as well as the degree of opposition or hostility being expressed.