Steven is an obvious choice. Their relationship has so much potential for growth and exploration in fanfiction. Steven's kindness and ability to forgive can really help Spinel on her journey of self - discovery.
A common plotline involves Spinel struggling to fit in on Earth, and Steven being her guide. He shows her the beauty of Earth and its inhabitants. This can lead to a deepening of their relationship as Spinel starts to trust and rely on Steven more. Another plotline could be Spinel having nightmares about her past, and Steven being there to comfort her, which further cements their bond.
The relationship in this fanfiction often explores themes of forgiveness and growth. Steven, with his nature of seeing the good in others, tries to help Spinel move past her pain. Spinel, who has been through so much, slowly starts to open up to Steven. It's a relationship that can be seen as a journey of two broken souls finding comfort in one another.
In many Steven Universe fanfics about Steven and Spinel, their relationship can be complex. Spinel was initially a villain but had a tragic backstory. Steven, being his empathetic self, often tries to understand her. In some fanfics, they form a deep friendship. Steven helps Spinel heal from her past traumas, and Spinel, in turn, might teach Steven something about himself or the world around him. It's a relationship full of potential for growth and mutual understanding.
In some fanfictions, Spinel might become more confident. After leaving her past behind, she could start to believe in herself more and not let others' opinions bring her down as easily.
One popular 'Steven x Spinel' fanfic is 'A New Beginning'. It shows an interesting take on how Steven and Spinel could develop a relationship post - the events in the show. It has great character development and a heartwarming plot.
A Steven x Spinel lemon fanfiction is likely to be a work that explores a romantic or perhaps more intense relationship between Steven and Spinel in a rather spicy or detailed way. However, such fanfictions often deviate from the original canon of the story. They can be interesting in terms of exploring different character dynamics and emotions that might not be shown in the official series. But they also might not be to everyone's taste as they can sometimes push the boundaries of what is considered appropriate in the context of the original work.
The fanfiction 'The Crystal Gems and Spinel' also features a great relationship between Steven and Spinel. In this one, they work together with the Crystal Gems to protect the Earth from a new threat, and their friendship blossoms during the process.
A really interesting plot twist in these fanfics can be when Spinel gets corrupted again, but this time Steven has to find a completely different way to heal her. It challenges his usual methods and tests their relationship. Another plot twist could be that Spinel starts to have dreams or visions about Steven's future, and she has to decide whether to tell him or keep it a secret. This can lead to a lot of internal conflict for Spinel and also affect her relationship with Steven in unexpected ways.