Formal:
* Je suis fier/fière de toi. (This is the most literal translation, meaning "I am proud of you.")
* Je suis très fier/fière de toi. (This emphasizes the feeling of pride.)
Informal:
* Je suis super fier/fière de toi. (This is a more casual way to express pride.)
* T'es vraiment super/génial/géniale! (This is a very casual way to express pride, meaning "You're really great!")
For a specific accomplishment:
* Je suis fier/fière de ce que tu as accompli. (This means "I am proud of what you have accomplished.")
Note:
* "Fier" is the masculine form, while "fière" is the feminine form.
* The pronoun "toi" is used when addressing a singular person informally, while "vous" is used formally.
* The context and your relationship with the person will determine the appropriate level of formality.