Antithetical (adjective)

Being in opposition or contrast to something.

Origin:

From greek antithesis, meaning "opposition, contrast".

Examples:

1. The two candidates hold antithetical positions on the issue.
2. The new policy is antithetical to the company's previous approach.
3. The concept of freedom is antithetical to that of oppression.
4. His ideas are antithetical to the core principles of the party.
5. The proposal was antithetical to the goals of the organization.