Explanation:

- Repudiate means to reject, refuse to accept, or disavow something.

- Option 1: Renounce – To renounce is to formally declare one's abandonment of a claim, right, or possession. It's similar to repudiating because both involve rejecting or giving up something.

- Option 2: Sanction – This usually refers to either a penalty for disobeying a rule (noun) or giving official permission or approval for an action (verb). It is not similar to repudiating.

- Option 3: Enforce – To enforce means to compel observance of or compliance with a law, rule, or obligation. This is the opposite of what repudiating means.

- Option 4: Regret – This is the feeling of being sorry or disappointed. It does not involve rejection or refusal.