Formal:
* Adonis: This refers to a Greek mythological figure known for his beauty, implying a more classical or idealized type of handsomeness.
* Beau: This means "handsome man" and is a slightly more formal term than some others.
* Heartthrob: This term implies a boy who is very attractive and desirable, often used for celebrities.
Informal:
* Cute: This suggests a more youthful and charming handsomeness.
* Good-looking: This is a general term for someone who is attractive.
* Hunky: This implies a more muscular and rugged handsomeness.
* Dashing: This suggests a charismatic and stylish handsomeness.
* Fine: This is a simple and direct way to say someone is attractive.
You could also use a phrase like "handsome young man" or "a boy with good looks." Ultimately, the best word or phrase depends on the specific context and the nuance you want to convey.