Formal:
* J'aime Amanda. (This is the most straightforward translation.)
* J'ai de l'affection pour Amanda. (This translates to "I have affection for Amanda" and is slightly more formal.)
Informal:
* Je suis amoureux d'Amanda. (This translates to "I am in love with Amanda" and is a more romantic way to say it.)
* J'adore Amanda. (This translates to "I adore Amanda" and is a strong expression of love.)
* Je t'aime, Amanda. (This translates to "I love you, Amanda" and is a very intimate and personal way to say it.)
Important Note: It's important to choose the expression that best fits the context and your relationship with Amanda.