First, give the OC a strong backstory related to the Uchiha clan's history. Maybe they were a survivor of the massacre or had a family member who was wronged. Second, develop their unique abilities. It could be a special form of the Sharingan or a new jutsu. Third, define their personality. A brooding and determined personality would fit well, as they are on a revenge quest.
First, focus on their initial reaction to being reborn as an Uchiha. Are they excited, scared, or confused? This will set the tone for their character development. For example, if they are excited, they might be more eager to explore their new powers and the Uchiha heritage right away.
Well, 'Rising Uchiha' is a cool Uchiha male OC fanfiction. The OC in it has a strong personality and his journey within the Uchiha clan is full of twists and turns. Then there's 'Uchiha in the Shadows' which shows an OC that has to navigate the clan's politics while hiding his true power. And don't forget 'The Uchiha Outsider' where the male OC is an outcast within the clan but manages to make a name for himself in a different way.
Revenge is also a frequent theme. Given the Uchiha's history in the Naruto series, an oc Uchiha in fanfiction might be on a quest for revenge against those who wronged the clan. This can lead to complex storylines where the character has to decide how far they are willing to go to get revenge and what the cost might be.
I'd recommend 'Madara and the Unseen Ally'. In this fanfic, the OC has a unique power that catches Madara's attention. The plot unfolds as they face various challenges together, and the writer does an excellent job of portraying Madara's character while also giving the OC a distinct personality.
One great Uchiha OC male fanfiction is 'The Uchiha's New Path'. It explores the journey of an original male Uchiha character in the Naruto universe. The story dives deep into his unique abilities and how he copes with the Uchiha legacy. Another good one is 'A Uchiha's Redemption'. It focuses on a male Uchiha OC who has made mistakes in the past and is trying to make amends, which makes for a very engaging read.
A popular 'Naruto Uchiha OC Fanfiction' is 'Uchiha's Redemption'. This fic focuses on an OC Uchiha who tries to redeem the Uchiha name after the clan's downfall. It delves deep into the Naruto universe's lore and the emotions of the OC are very well - portrayed. The story also has some great fight scenes that are exciting to read.
To make the OC believable, give them relationships. They could have friends or enemies outside of Madara. These relationships will shape their character. For example, if they have a best friend who was killed by a rival clan, it could fuel their desire to get stronger. Also, let their character develop over time. Don't make them perfect from the start. They should learn from their experiences, especially those involving Madara. Maybe at first they idolize him, but as they see his darker side, they start to question his methods.
One great Uchiha OC male self - insert (SI) fanfiction is 'The Uchiha's New Path'. It has an interesting plot where the male OC, who is inserted into the Uchiha clan, tries to change the fate of the clan. The character development is well - done and the story follows the Naruto universe's lore quite closely.
In a fanfiction, an OC Uchiha born with an activated Sharingan could face unique challenges. The Sharingan drains chakra, and being born with it activated might mean they have to learn early on how to manage their chakra levels more effectively. Also, they could attract unwanted attention, either from jealous clan members or from enemies who see them as a threat due to their special ability.