One common theme is redemption. A character who has made mistakes in the original story gets a second chance to make things right. Another theme is love. For instance, a couple that broke up in the original plot gets a second chance at their relationship.
Well, a frequent theme is forgiveness. Snape has to seek forgiveness from those he wronged in his previous life. Also, the theme of changing fate is quite common. He tries to change the outcomes that were not so good in his first life. And there's the theme of growth. He grows as a person, learning from his past errors and becoming a better version of himself. This is often shown through his interactions with other characters in the fanfiction.
Redemption is a big one. Characters who have made mistakes or been on the wrong side are often given a chance to make up for it. Another theme is hope. It's about believing that things can be better even after a lot of bad has happened, like a planet recovering from war or a character overcoming their dark past.
Love and self - discovery are also prevalent. She gets a second chance to understand herself better and find a more fulfilling love. For example, she might realize what she truly wants in a relationship that she didn't before.
Love is also a prevalent theme. In many 'a second chance novels', love gives characters the impetus to change and seek a second chance. For example, in 'Jane Eyre', Jane gets a second chance at love and a new life when she reunites with Mr. Rochester.
The theme of changing fate is also prevalent. Naruto tries to change the destinies of his friends and the whole shinobi world. He doesn't want to see the same tragedies occur again. Also, self - discovery is a theme. As he changes things, he also discovers new aspects of himself and his capabilities. He might realize he could have been a better leader earlier if he had known certain things.
Redemption is a common theme. Since Tony gets a second chance, he often tries to fix his past wrongs, whether it was a mistake in a relationship or a strategic error. Another theme is self - discovery. Through time travel, he gets to see different versions of himself and understand who he really is.
Love is a common theme. Characters often get a second chance at love, like in 'The Bridges of Madison County' where the two main characters have a brief, intense encounter and later might get a second chance at that relationship. Another theme is redemption. For example, in 'Les Misérables', Jean Valjean is given a second chance at life and tries to redeem himself.
Redemption is a common theme. Characters often try to make up for past mistakes. For example, if a character was a bad friend in their first life, in the second chance, they strive to be a better one.
Another theme is self - discovery. As they are given this second chance, they start to explore who they really are outside of the Sith ideology. They question their beliefs and values that they held while being a Sith.
Redemption is a common theme. Bilbo might have made mistakes or had regrets in the original story, and in these fics, he gets a chance to make things right.