A human scientist. She could be studying Cybertronian technology and in the process, get to know Optimus Prime. Her inquisitive nature and thirst for knowledge, combined with Optimus Prime's respect for those who seek understanding, could lead to a romantic relationship.
A strong female Autobot would be a great love interest. They already share the same values and goals, and the bond of being on the same side in the fight against the Decepticons could easily turn into a deeper emotional connection.
An alien diplomat could be a good match. This character could bring a different perspective to Optimus Prime's world. They could meet during some inter - galactic peace negotiations, and the diplomat's charm and intelligence might attract Optimus Prime, leading to love.
A possible love interest could be another Autobot. Maybe a female Autobot with whom he has fought side by side for a long time and gradually developed feelings for. Another option could be a human female who has shown great courage and understanding, and through their interactions, Optimus Prime finds himself attracted to her.
It could be Lillie. She is kind - hearted and has a deep connection with Pokémon. She and Ash have had many adventures together in Alola already. Her gentle nature and her growth throughout the series could make her a great love interest for Ash.
One possibility could be a young girl who accidentally stumbles into his realm. She might be different from others, with a kind heart that catches Slender Man's attention. Maybe she's not afraid of him at first sight, which intrigues him.
One potential love interest could be a half - elf. They would bring a unique blend of both elven and human qualities, which might intrigue Thranduil. Or it could be a nature spirit. Since Thranduil has a strong connection to the forest, a nature spirit who embodies the essence of the forest could be a fascinating match for him. Also, a powerful sorceress from a far - off land might be his love interest, with her magic and mystery attracting him.
A plot could be that Optimus Prime, in his travels, discovers a lost civilization. There, he meets a female leader who is intelligent and kind. She is intrigued by his noble nature, and he by her leadership and the unique culture of her people. As he helps her protect her civilization from various threats, their relationship blossoms into love.
His love interest could be Wendy's sister. In some fanfictions, a sister of Wendy who was always a bit more curious about Neverland than Wendy herself could be the one Peter Pan falls for. She might be more daring and willing to fully embrace the wildness of Neverland, which attracts Peter.
A mortal could also be a good love interest. Imagine Nico, who has been so involved in the world of gods and demigods, falling for a normal human. This mortal could be an artist or a scientist, someone who sees the world in a completely different way than Nico. Their relationship could be about Nico learning about the mortal world through this person's eyes and falling in love with both the person and the new perspective.
Arcee might also be a candidate. She is a strong and independent Autobot. A fanfiction could depict a love story where Optimus Prime and Arcee start off as comrades in arms and gradually develop deeper feelings. Their relationship could be complicated by the constant threat of war and the need to make sacrifices for the greater good of the Autobot cause.
Irene Adler could be a great love interest. She's smart, cunning, and was able to outwit Sherlock once. Their relationship in the original stories had a certain tension that could be developed into a full - blown love story in a fanfiction. She challenges him and has her own secrets, which could make for an exciting dynamic.
Sasori could be an interesting love interest. They are both from Akatsuki and have a certain connection through their art, though Sasori's is more in the form of puppets and Deidara's is explosive art. Their different personalities could create a lot of tension and a unique love story.