The word "letted in" is not a commonly used phrase, therefore searching for antonyms of this term may be irrelevant. However, assuming that "letted in" refers to giving permission to enter, its antonyms may include deny entry, withhold access, refuse admission, or prohibit entry. These terms imply the act of declining or preventing someone from accessing a specific place or activity. It is essential to note that allowing entry does not always mean approving or supporting the action being taken, but it can be a way of acknowledging someone's right to be present. Therefore, in some situations, denying entry may be necessary to ensure safety, security, or compliance with rules and regulations.