Formal:
* J'aime Andrew. (This is the most literal translation, but it's a bit stiff and formal.)
Informal:
* J'adore Andrew. (This is a more affectionate way to say "I love Andrew" and is often used with friends and family.)
* Je suis amoureuse d'Andrew. (This is a more romantic way to say "I love Andrew" and is typically used for a significant other.)
Other options:
* Je t'aime, Andrew. (This is a very romantic way to say "I love you" and is best used for a close relationship.)
Ultimately, the best way to say "I love Andrew" in French depends on the context of your relationship with him.