class

a second-class citizen

someone who is treated as if they are less important than other people in society. Although she was married to an Australian, Louise couldn't get a work visa and it made her feel like a second-class citizen.

---

in a class by itself

the best or only one of its kind. The High Desert Museum was in a class by itself.

Usage notes: also used in the form in a class by yourself: Among jazz singers, she was in a class by herself.