"Standbyes" is a plural noun that usually refers to a reserve or backup system or device that can be used in case the primary one fails. The antonyms for "standbyes" could be various, depending on the context, but some possible ones include active, in use, operational, primary, main, dependable, reliable, essential, necessary, and critical. For example, if we talk about a backup generator that is always ready to provide power in case of a blackout, its antonym could be the main power grid that is constantly supplying electricity to the building. Similarly, if we refer to standby employees who are ready to replace absent or sick ones, their antonyms could be permanent or full-time staff who are always present and productive.