There is often a theme of transformation. Shredder might transform his evil ways, or April might be transformed in some way by her association with Shredder. Additionally, the theme of sacrifice can be present. One of them may have to sacrifice something, like their loyalty to their respective sides or their own personal goals, for the sake of their relationship. And the exploration of the 'otherness' of their relationship, as it goes against the norm of the source material, is also quite common.
One great place to start looking for Shredder x April fanfiction is Archive of Our Own (AO3). There are numerous works there that explore different aspects of this pairing. Some might focus on a more angsty relationship, while others could be set in alternate universes where their relationship takes a different turn.
One common theme is redemption. Many fanfics explore the idea of Shredder seeking redemption in April's eyes, like how he might try to atone for his past wrongs. For example, in some stories, he protects April from other threats, which is a way of showing his change.
I'm not sure specifically as it could be about many things. 'April' might be a character name, and'shredder' could be some kind of entity or character too. A 'fanfic' is a fan - created fictional story, so it could be a story created by a fan that involves these elements in some unique plot.
One great Shredder and April fanfiction is 'The Unlikely Alliance' which explores an alternate universe where they have to team up against a greater threat. It has some really interesting character development for both of them.
You could start by looking on popular fanfic websites such as Archive of Our Own (AO3) or FanFiction.net. Just search for 'april shredder' on their search bars and see if any relevant fanfics come up.
The contrast between them. Shredder is this menacing, power - hungry villain and Leonardo is the noble and disciplined hero. Their interactions can be full of tension and drama.
One common theme is the conflict between their two different natures. Shredder is often portrayed as the villain, and Leo as the hero. So, there's a push - pull dynamic of good vs. evil.
A 'Donnie x April Kiss Fanfiction' might explore the relationship between Donnie and April in a romantic context. It could delve into their characters' growth through this new aspect of their relationship. For example, Donnie might become more confident and April could become more open about her feelings.
In TMNT x April fanfiction about bullying, it could be that April is being bullied at school and the Turtles come to her rescue. For example, they might use their ninja skills to secretly protect her from the bullies without her even knowing at first. This adds an interesting dynamic to their relationship as it shows the Turtles' loyalty and care for April.