Formal:
* Eu amo você: This is the most common and direct translation, suitable for formal situations.
* Eu o/a amo: This is a more formal way to say "I love you" when addressing someone specifically.
Informal:
* Eu te amo: This is the most common way to say "I love you" in an informal setting.
* Amo você: This is another informal way to say "I love you".
* Eu gosto muito de você: This translates to "I like you very much" and can be used as a more casual way to express love.
Other options:
* Eu te adoro: This translates to "I adore you" and is a stronger expression of love.
* Eu sou apaixonado(a) por você: This translates to "I am in love with you" and is a more romantic expression.
The best way to say "I love you" in Portuguese will depend on the specific context and your relationship with the person you are speaking to.