Fore-warns is a term used to describe giving someone advance notice or alerting them about something before it happens. The antonyms for fore-warns would be to surprise, ambush, catch off-guard, or shock. It's the opposite of forewarning someone of a forthcoming event or action. Instead, these antonyms imply taking someone by surprise or leaving them unprepared. In certain scenarios, forewarning people can be beneficial, but in others, keeping things secret or surprising them can be preferable. So, the selection of the antonym for fore-warning would depend on the situation and its requirements.