Formal:
* Adiós: This is the most common and formal way to say goodbye.
* Hasta luego: This means "until later" and is a slightly more informal version of adiós.
* Hasta pronto: Means "until soon."
* Hasta la vista: Means "until I see you."
* Buen día: This means "good day" and is a polite way to say goodbye in the morning or afternoon.
* Buenas tardes: Means "good afternoon" and is used in the afternoon.
* Buenas noches: Means "good night" and is used in the evening.
* Que tenga un buen día/tarde/noche: Means "have a good day/afternoon/night" and is a very polite way to say goodbye.
* Que le vaya bien: Means "have a good day/afternoon/night" and is another polite way to say goodbye.
* Hasta la próxima: Means "until next time."
* Nos vemos: Means "we'll see each other."
Informal:
* Chao: This is a very informal and common way to say goodbye, similar to "bye" in English.
* Ciao: Similar to "chao" but Italian in origin.
* Hasta mañana: Means "until tomorrow."
* Nos vemos luego: Means "see you later."
* Te veo: Means "see you."
* Cuídate: Means "take care."
* Que te vaya bien: Means "have a good day/afternoon/night."
* Un abrazo: Means "a hug" and is a very affectionate way to say goodbye.
* Beso: Means "kiss" and is another affectionate way to say goodbye.
Adding Nuance:
You can also add nuance to your goodbye by using phrases like:
* Nos vemos pronto: "See you soon."
* Que tengas un buen viaje: "Have a good trip."
* Que tengas un buen fin de semana: "Have a good weekend."
* Me alegro de haberte conocido: "I'm glad to have met you."
Remember: The best way to say goodbye in Spanish depends on the context, the relationship you have with the person you are saying goodbye to, and the formality of the situation.