The plot should be engaging. A good crossover fanfic will have a plot that combines the elements of both universes in a seamless way. For instance, if it's Dexter crossing over with a fantasy world, the mystery or crime aspect of Dexter's world should blend well with the magic or other elements of the fantasy world.
Consistency in Dexter's character traits. His 'dark passenger' and his moral code (however twisted it may be) should be maintained. If he suddenly starts acting completely out of character just for the sake of the crossover, it's not a good fanfic. Also, the fanfic should offer something new, like a new perspective on Dexter or a new type of case he has to solve because of the crossover.
First, look for how well the two universes are merged. For example, if it's a Witcher 3 and Harry Potter crossover, see if the magic systems are explained in a way that makes sense. Second, the characterization. Geralt should still act like Geralt. Third, the plot. It should be engaging and not just a random mash - up of the two worlds.
First, look for a well - written Sesshomaru. He should be in - character, not just a shell of his original self. The world - building of the crossover is crucial too. For instance, if it's a crossover with a different anime, how the two worlds blend together seamlessly. Another aspect is the relationships. How Sesshomaru interacts with the new characters from the other universe, whether it's a friendship, an alliance or a rivalry.
The plot needs to be engaging. A good Buffy crossover fanfic will have a plot that makes sense for both universes. It can't just be a random mash - up. For instance, if it's a Buffy and Star Trek crossover, the reason for their meeting should be related to a significant threat that both universes can be involved in.
The respect for the source materials is crucial. The Witcher has its own lore, and so does the other universe in the crossover. For example, in a Witcher and Warcraft crossover, the author should not distort the basic concepts of either. The development of new relationships is also something to look for. How do the characters from different universes form bonds or rivalries? And the creativity in combining the magic or abilities from both universes, like in a Witcher and Final Fantasy crossover, is also very important.
The exploration of new themes is also important. In a cyberpunk and Tolkien crossover, you might see how the cybernetic enhancements in cyberpunk contrast with the more natural and magical elements of Middle - earth. And of course, a good plot. It should keep you engaged, whether it's about a character trying to save both worlds from a common threat or something else entirely.
Character interactions are key. You want to see how the characters from different shows blend together. For example, if it's a crossover with Scooby - Doo, seeing how Shaggy and Dipper would react to the mysteries in Gravity Falls. Also, a good plot that makes sense for both universes. It can't just be a random mash - up.
One more element to consider is the originality of the concept. A lot of fanfics can be repetitive, but a great 'villan naruto crossover fanfic' will have a fresh take on things. Maybe it's a unique combination of villains or a new spin on Naruto's powers in relation to the villains. It could also be a different time period in the Naruto world where these crossovers occur, like a pre -shinobi era Naruto dealing with modern -day villains. This kind of creativity makes the fanfic stand out.
One key element is how well the two universes are blended. For example, if it's a RWBY and Marvel crossover, the powers and personalities of the Marvel characters should fit well into the RWBY setting. Another is the plot. It should be engaging and not just a simple mash - up. For instance, a good plot could involve a common threat that both universes need to face together.
A good Danny Phantom crossover fanfic should have a well - developed plot that combines the two universes in a logical way. For example, if it's a crossover with Teen Titans, the reasons for Danny and the Titans to meet and work together should make sense.
Character interactions are key. You want to see how the Final Fantasy 15 characters react and form relationships with characters from the other franchise in the crossover.