Informal:
* Il me manque: This is the most common and direct translation, meaning "He is missing to me."
* Je l'aime beaucoup: This translates to "I love him a lot" and can imply that you miss him.
Formal:
* Je ressens son absence: This is more formal and means "I feel his absence."
Other options:
* J'ai envie de le voir: This means "I want to see him," and can be used to express missing someone.
* Je pense beaucoup à lui: This translates to "I think about him a lot," and can be a way to say you miss him.
The best translation for "miss him" will depend on the specific situation and the relationship between you and the person you are speaking to.