* Goodbye: If you're using "hi" as a greeting, the opposite would be a farewell like "goodbye" or "see you later."
* Bye: This is a more casual version of goodbye.
* Low: If you're using "hi" to refer to something being high, the opposite would be "low."
* Bye-bye: This is a playful and informal way to say goodbye.
* Ciao: This is an Italian greeting that can be used as both a hello and a goodbye.
It really depends on what you are trying to convey!