Formal:
* Atentamente, (Sincerely) - The most formal closing.
* Con mi más cordial saludo, (With my warmest regards) - A slightly less formal option.
* Un cordial saludo, (Warm regards) - Another suitable formal closing.
* Reciba un cordial saludo, (Please accept my warm regards) - This adds a bit of formality.
* Le saludo atentamente, (I greet you sincerely) - A good choice for someone you don't know well.
Informal:
* Un abrazo, (A hug) - A very common and friendly ending.
* Con cariño, (With love) - A closer, affectionate ending.
* Saludos cordiales, (Cordial greetings) - A friendly but still somewhat formal option.
* Hasta pronto, (See you soon) - Great if you hope to write again soon.
* Te mando un beso, (I send you a kiss) - A very affectionate ending.
More casual:
* ¡Nos vemos pronto! (See you soon!) - This is more of an exclamation than a closing.
* ¡Mucha suerte! (Good luck!) - A nice option for someone who's going through something.
Always sign off with your name:
* [Your Name]
Example:
* ¡Hola [Pen Pal's Name],!
* ¿Cómo estás?
* ... [Rest of your letter] ...
* Espero que te encuentres bien.
* Un abrazo,
* [Your Name]
Important Note: The level of formality you choose will depend on your relationship with your pen pal. If you're writing to someone older or someone you don't know very well, use a more formal closing. If you're writing to a friend, you can use a more informal closing.