The wizard or mage characters are also common in slime fanfic. They might be the ones who created the slime through a spell, or they could be trying to use the slime's powers for their own gain. Their knowledge of magic adds an interesting element to the story.
In some slime fanfics, there are magical girls or boys who encounter the slime. These characters are popular as they bring their own set of powers and personalities to the story. They might initially be scared of the slime but then learn to work with it.
Rimuru Tempest is an obvious choice as he is the main character in the original series. He has a lot of potential for further development in fanfics. Veldora is also popular. His powerful dragon form and his comical personality can add a lot of fun elements to the story. And Shizu, her backstory and connection to Rimuru make her a great character to include.
Another possible main character could be an antagonist. This could be a powerful entity that opposes the slime's progress in the gamer world. It could be another slime that has turned evil or a more traditional fantasy villain like a dragon or a dark sorcerer.
Rimuru is a must - include character. As the main character in the original work, he can be the central figure in fanfiction too, with new adventures or relationships. Another popular one is Veldora. His powerful and somewhat comical personality can add a lot of fun elements to the fanfiction.
Veldora is another favorite. His power and his somewhat comical yet powerful nature make him interesting in fanfiction. There could be stories where he takes on a more mentoring role to Rimuru or gets involved in unexpected adventures.
Another idea is a slime oc in a modern city setting. It could be trying to fit into human society, perhaps getting a job or going to school. There could be humorous situations like the slime oc trying to understand human customs and technology.
Often, original characters that are powerful yet have a mysterious backstory tend to be popular. For instance, a character who is a powerful mage but has a past linked to a long - lost magic artifact. They add an element of intrigue to the fanfiction.
The young and talented boxer is also a common character. This is the one with natural athletic ability, a lot of heart, but still has a lot to learn. He might have a troubled past or a big dream, and the story usually follows his journey in the boxing world, from small local fights to bigger championships.
Salaar himself is of course a very popular character in Salaar fanfic. Writers often delve into his psyche and his journey.
Neo is definitely a popular character in matrix fanfic. Writers often continue his story, exploring his further development of powers or his role in new threats to the Matrix. Trinity is also quite popular. Fans might write about her relationship with Neo in different scenarios or her own solo adventures within the Matrix. Morpheus is another one. His wisdom and leadership make him an interesting character to build stories around in fanfic, like his search for new knowledge about the Matrix or training new recruits.
One popular character might be the Ember Guardian. This character is often depicted as having the ability to control the most powerful embers and is seen as a protector of the embers' realm.