Question: It’s the highlight of all stories when protagonists will corner to choose a critical decision, like in Star Wars, Luke wants to bring Vader back to light side and must confront him but if he’ll do, he might use his anger facing his father, he might harm him and become a sith, but if he won’t, his father might be totally defeated by the dark side and Palpatine’s empire will continue to reign. The same thing in Hunger Games, when the game committee announces that there should be only one winner, Katniss get trouble if she’ll select the victory and will kill Peeta whom she had an emotional attachment with. I would like the character's dilemma in my novel to be effective and believable, in creating on it what must I consider?Answer:
What you're describing is the main character's personal crisis, which is part of the main character throughline, a series of events that illustrate the main character's inner conflict.
Your main character will begin the story with a particular way of doing things or solving problems. This initial approach then comes under pressure, usually because of an impact character who has a different approach. The impact character forces the main character to consider whether his approach is the best.
The main character's crisis is the moment when he/she ultimately decides whether to change and adopt the impact character's approach or stay with (perhaps double down on) his original approach. Whatever choice the main character makes, right or wrong, will determine if he is able to achieve the story goal.
To take the examples you cite...
In Return of the Jedi
, we see Luke initially as the embodiment of Jedi values. Then he is pressured by Darth Vader to switch to the dark side. This reaches a crisis when Vader threatens to attempt to turn Leia to the dark side. Luke makes his ultimate decision to remain
steadfast when he refuses to kill Vader and tosses aside his light sabre. Because of this choice, Vader and Luke together are able to defeat the Emperor.
In The Hunger Games
, Katniss begins the story as someone who has learned to suppress certain aspects of herself and her humanity in order to survive. For instance, when her sister brings home a kitten, Katniss's first reaction is to drown it rather than have another mouth to feed. After the reaping, she lets herself be changed and controls her behaviour in order to survive the Games. Peeta, however, offers her a different perspective. He doesn't want the Games to change him. In other words, he feels that it's not really survival if you lose your humanity in the process. When Rue dies, Katniss remember's Peeta's words and chooses adapt his approach. She honours Rue's body, even though it will earn her the Capitol's rath and later refuses to kill Peeta. As a result, she survives and retains her humanity (though she earns the Capitol's displeasure).
Bottom line: you have to consider the main character's decision as part of a complete arc. It cannot be something that comes out of nowhere.
You should show who the main character is in the beginning and how they are pressured to change. Then you can show their decision and its aftermath -- whether that decision was good or bad for the main character personally, whether it leads them to inner peace, contentment, or happiness. You also should show that their choice determines whether they achieve the story goal.
It also helps to develop your impact character throughline. Make your impact character someone who can really pressure the main character to change, so that the reader can feel the main character's dilemma. It helps if the reader cannot be certain ahead of time what the right decision will be or whether the main character will make the right decision.