The main characters might be individuals who have had some sort of significant event in their lives that made them have these words they wish they had said. It could be a young person who was too shy to speak up to a bully, or an adult who failed to communicate their true feelings to a family member during a crucial moment. There could also be a character who is on a journey to find the people they should have said these words to and make amends.
It might be centered around the idea of things left unsaid. Maybe the characters in the novel have a lot of emotions and thoughts that they never got around to expressing, and the story delves into how that affects their lives and relationships. For example, it could be about a lost love where the protagonist had so many things they wanted to tell their partner but never did, and now they are living with the consequences of that silence.
As I haven't read 'the wish novel', I can't be certain about the main characters. However, it's common in novels for there to be a central character who is on a journey, perhaps a person with a strong will and a big wish. There might also be supporting characters like family members or antagonists who oppose the main character's wish.
Since I don't know the exact 'a wish novel', I can't say for sure. But it could be a young protagonist who is on a quest related to wishes.
There might be a group of friends as the main characters. They could all have different wishes on the list, and through their interactions and shared adventures in trying to fulfill the wishes, their relationships could develop. For example, one friend might wish for a career opportunity and another for a romantic relationship, and their combined efforts to achieve these wishes could form the core of the story.
Without having read the book, it's impossible to be certain. But it might have a hero or heroine who is on a quest related to their great wish. There could also be supporting characters like friends or family members who either help or hinder the main character in achieving their wish.
Often, there is a protagonist who is driven by a strong sense of vengeance or a need to fulfill a certain goal related to their 'death wish'. There might also be an antagonist who stands in the way of the protagonist's pursuit.
In 'the last wish novel', apart from Geralt, Yennefer and Ciri, there are other notable characters. Dandelion, for instance, is Geralt's friend. He is a bard and often gets involved in Geralt's adventures, sometimes causing trouble but also providing some comic relief. Another character is Vesemir, an older Witcher who serves as a mentor to Geralt and the other Witchers at Kaer Morhen.
In 'the wish of the dragon novel', the main characters could include the dragon of course. There may be a wizard or sorcerer who has some connection to the dragon's wish, either helping or trying to manipulate it. And perhaps a young adventurer who stumbles upon the dragon's situation and gets involved in the quest related to the dragon's wish.
Since I don't know the specific 'last wish system novel', I can't tell you the main characters. But usually, there would be a protagonist who is closely involved with the last wish system. There might also be an antagonist who tries to disrupt or misuse the system.
Since I haven't read 'her last wish novel', I can't be certain about the main characters. But if we think about typical stories, the main character is the one with the last wish. She might be a young woman, or an older one. There could be a mentor - like figure, someone with more life experience who gives her advice on how to go about fulfilling her wish. And of course, there could be characters related to her personal life, like a mother or a sister, who play important roles in either supporting or opposing her last wish depending on their own motives and relationships with her.