Many of the characters in Tender is the Night act in extreme ways that are virtually impossible to look past. Devereux Warren is the most extreme example of this. He rapes his daughter Nicole when she is a young teen, right after her mother dies. Even before we know this, Nicole is a fairly sympathetic, though hard-to-get-to-know character. Yet, when she tries to kill her husband and her children, even though she remains sympathetic, arguably, her actions mark her as seriously dangerous. Dick has his ups and downs in the text, but until he leaves town, he’s still the guy you can count on to help when you get in a jam. Like when he bails Mary and Carolyn out of jail even though they’ve both been jerks to him. Also, Dick drinks a lot. This action comes to define him as no longer "serious," and no longer fit to practice.
Occupation is a big one in Tender is the Night. Dick is a psychiatrist, and when he stops practicing, his insight and knowledge of the human mind turns dark as he "works over" the people he’s drawn into his circle. Nicole has no occupation, other than perhaps mental patient, even though she makes it clear she wants to work at something meaningful. Her lack of occupation defines her as unfulfilled. Tommy is a soldier, and at least until he and Nicole get together, he even considers war his home. Albert McKisco is really defined by his occupation. When he’s a struggling novelist, he’s not a nice person. When he’s a successful novelist, he suddenly becomes a nice person. Rosemary is an actress and for much of the novel considers life to be her own personal melodrama.