Formal:
* Adorable: This is the most direct translation, but it's not as commonly used as the other options.
* Encantador/a: This means "charming" and is a good choice for a person or something that is aesthetically pleasing.
Informal:
* Monísimo/a: This is the most common and casual way to say "adorable." It literally means "very cute."
* Guapísimo/a: This means "very handsome/beautiful" and can be used for someone or something that is very attractive.
The best option will depend on the specific situation and the tone you want to convey.