Formal:
* Com amor: This is the most common and general way to say "with love." It's appropriate for almost any situation.
* Com carinho: This translates to "with affection" and conveys a softer, more tender feeling.
Informal:
* Com amor: You can use the same phrase as in the formal setting, but it's also common to shorten it to "amor" or "com amorzinho" (with little love).
* Com carinho: This is also used informally, with the same meaning as the formal version.
* Com muito amor: This means "with a lot of love" and emphasizes the intensity of your feeling.
In a letter or note:
* Com amor, (Your Name) - This is a common way to sign off on a letter or note.
* Com carinho, (Your Name) - This is another common way to sign off, especially if you're writing to someone you know well.
The best option for you will depend on the specific situation.