In a love story, a great plot twist is when the person who has been secretly in love and helping the protagonist all along is revealed to be the one they should truly be with, instead of the one they thought they loved. For example, the best friend who has always been there in the background, but the main character was too blind to see their real feelings until some event makes it clear.
One good plot twist could be that the two characters who seem to be falling in love are actually long - lost siblings. It completely changes the dynamic of their relationship from romantic to a more complex family - oriented one.
One good plot twist could be that the character who seems to be the hero is actually the villain all along. For example, in a detective story, the detective who has been leading the investigation turns out to be the mastermind behind the crimes he's supposed to solve. It completely flips the reader's expectations.
One of the best plot twists is in 'Gone Girl'. The wife fakes her own death and frames her husband, completely turning the typical 'missing wife' love story on its head. It shows that not all love is as it seems and there can be dark, manipulative sides to relationships.
One good plot twist could be that the person the main character thought was their soulmate turns out to be a long - lost relative. It completely changes the dynamic of the relationship and adds a whole new layer of complexity and drama. For example, they might have been on the verge of getting married when this revelation comes to light.
The discovery that the entire world the characters live in is a simulation. In a short science - fiction story, the characters are going about their normal lives until they start to notice glitches in the world around them. As they dig deeper, they find out that their whole existence is just part of a complex computer - generated simulation, which turns their understanding of reality upside down.
A plot twist could be that the love between two characters was actually a spell cast by a jealous third party. When they find out, they have to decide if their feelings are real or just the result of magic. This adds a magical and moral dilemma to the love story.
One plot twist could be that the girl in the fanfic, who is in love with Austin, suddenly discovers that Austin has a secret twin brother. And she gets confused about her feelings as the twin brother also shows interest in her.
Character development plays a role too. If a character has a hidden side that is revealed as a plot twist, it should be consistent with their previous actions and personality to some extent. For example, in 'Shutter Island', Teddy's true identity as a patient rather than an investigator is a major plot twist. But looking back, his strange experiences and mental states on the island can be seen as clues, and his character's journey makes the twist feel more earned.
One good twist could be a character who seems to be the villain turns out to be the hero all along. For example, in a detective story, the suspect who has all the signs pointing to him as the killer is actually trying to protect the real victim from a more dangerous threat.
One great story with a good plot twist is 'The Sixth Sense'. The twist that the main character is actually dead all along completely changes the viewer's perception of the whole movie. It's a brilliant psychological thriller.
One good plot twist could be that the main character, who has been searching for a missing heirloom throughout the story, discovers that it was in their possession all along, hidden in a place they never thought to look. Maybe it was inside an old family photo album that they never fully explored.