The word "allowed" has a few antonyms, all of which carry their own nuances. "Prohibited" is perhaps the most straightforward antonym, indicating that something is completely disallowed with no room for negotiation. "Restricted" suggests that while something may still be allowed, there are certain limitations or conditions that must be met first. "Denied" implies that permission has been specifically withheld, and "forbidden" connotes a sense of taboos or moral imperatives against a particular action. Ultimately, the choice of antonym will depend on the context and severity of the act in question, as well as the personal values and beliefs of the person making the decision.