Informal:
* Eu sou demais! (This is the most common and informal way to say it.)
* Eu sou incrível! (This is another informal option, meaning "I'm incredible!")
* Eu sou foda! (This is a very informal and slangy way to say it, meaning "I'm awesome/badass".)
Formal:
* Eu sou extraordinário/extraordinária! (This is a more formal way to say "I'm extraordinary.")
* Eu sou fantástico/fantástica! (This is another formal option, meaning "I'm fantastic.")
Other Options:
* Eu sou muito bom/boa! (This translates to "I'm very good," which can be interpreted as "I'm awesome" depending on the context.)
* Eu sou um/uma gênio! (This translates to "I'm a genius," which can be used in a playful way to mean "I'm awesome.")
Remember to choose the phrase that best suits the situation and your relationship with the person you're talking to.