The tycoon himself is an important character. He is the central figure around which the story revolves. There is probably also his love interest, who adds a different dimension to the story, often challenging his values and priorities.
Well, there could be the tycoon's business rivals. They are important as they create the conflict in the story. Their actions and decisions force the tycoon to make his own moves. Also, there might be some loyal employees or assistants of the tycoon. They help him run his business empire and also offer different perspectives on his actions.
The main character in 'The Last Tycoon' novel is Monroe Stahr, a powerful Hollywood tycoon. He is a man with great vision and determination in the movie business. Kathleen Moore is a key female character. Their relationship is a central part of the story. Additionally, there are a host of other characters that populate the Hollywood world of the novel. These include producers, directors, and actors who all interact with Stahr. The studio workers also play a role in depicting the environment and the challenges that Stahr faces in his quest to maintain and expand his Hollywood empire.
The protagonist is surely an important character. He is the one who faces the last temptation and his journey forms the core of the story.
Rey is very important. She's a strong Force - user and her growth in the Force is a major part of the story. Finn is also crucial. He has a unique perspective coming from being a former stormtrooper and is now fighting for the Resistance.
I don't know specifically since I haven't read it, but usually there are protagonists who drive the story forward.
Harry Black is an important character. He is sort of a central figure in the web of stories within the novel. His actions and experiences are used to show different aspects of the urban life in Brooklyn.
Hawkeye is the most important character. He is a skilled frontiersman. Chingachgook, one of the last Mohicans, is also very important as Hawkeye's friend. And Uncas, Chingachgook's son, is another key figure in the story.
Perhaps there is a family member, like a grandchild or a niece/nephew who has a special connection with Ptolemy Grey. This person could be important in terms of the emotional support they give or the way they help him face his last days. And there could be a doctor or a medical professional who is involved in his care.
Indiana Jones is obviously very important. His father, Henry Jones Sr., is also crucial as his disappearance drives much of the story. The Nazis are important as the antagonists. And there are some side characters in the various locations they visit who help or hinder Indy in his quest.
I'm not sure exactly without reading it, but likely the last tycoon would be a main character. And there would probably be a female love interest, as is common in many novels of that era.
There are several important characters. Aang is the central figure. He's the one who has to bring balance. Katara is crucial as she's not only a waterbender but also a great friend and support to Aang. Sokka may not be a bender, but his intelligence and skills are valuable. Prince Zuko has a complex character arc. He starts as an antagonist trying to capture Aang for his own redemption in the eyes of his father, but later he changes. Also, Toph, the earthbender, is an important addition later in the story as she helps Aang with his earthbending training.