Formal:
* Jesteś ładna/ładny. (You are beautiful/handsome.)
* Jesteś piękna/piękny. (You are beautiful/handsome.)
* Jesteś atrakcyjna/atrakcyjny. (You are attractive.)
Informal:
* Jesteś śliczna/śliczny. (You are pretty/handsome.)
* Jesteś ładna/ładny. (You are pretty/handsome.)
* Jesteś fajna/fajny. (You are cool/nice.)
More specific:
* Masz ładne oczy. (You have beautiful eyes.)
* Masz ładny uśmiech. (You have a beautiful smile.)
* Masz ładne włosy. (You have beautiful hair.)
Important Note:
* "ładny" is used for both masculine and feminine nouns, but "ładna" is used for feminine nouns only.
* "piękny" is used for both masculine and feminine nouns, but "piękna" is used for feminine nouns only.
Remember that it is always polite to be respectful when complimenting someone's appearance. Consider the context and the relationship you have with the person you are talking to.