Perhaps a Saiyan female. Since Broly is a Saiyan, it would make sense for him to be paired with someone from his own race. They could bond over their Saiyan heritage and power.
It could also be a fellow warrior from a different race who respects Broly's strength. They meet on the battlefield and, over time, their mutual admiration turns into love. Maybe a female fighter from a race that is also known for its combat skills, like the Androids in the Dragon Ball series. Their relationship could be based on sparring, training together, and gradually realizing they have deeper feelings for each other.
A new Bakugan trainer in town could be his love interest. She's fresh, full of energy and her unique Bakugan battling style catches Ace's eye.
It could be one of his female classmates. In the Clannad world, there are many female characters around Sunohara in school. Maybe a girl who is initially annoyed by his boisterous behavior but later comes to see his good side.
Maybe a new character, like a mysterious meister who arrives in Death City. She could have unique powers and a personality that attracts Death the Kid. Since Kid is so into symmetry, she might have some symmetrical features or abilities that draw his attention at first, but then her inner self is what really makes him fall for her.
Perhaps a scientist who is working on a related project. She would be attracted to Chase's intelligence and his bionic abilities. And Chase would be drawn to her knowledge and her determination in the scientific field. They would start collaborating on projects and slowly fall in love.
Maybe Rukia could be a potential love interest. She has a strong connection to the world that Urahara is a part of. They both have a deep understanding of the Soul Society and its workings, which could form the basis of a romantic relationship.
A strong possibility could be Misty. They've been traveling companions for a long time. Misty has shown care and concern for Ash over the years, and there have been moments that could be seen as the start of a deeper connection.
Perhaps a girl from a different town who comes to compete in Hiro's town. She has a different style of Beyblading. Hiro is intrigued by her and as they interact more, they find out they have a lot in common and fall in love.
A kind - hearted doctor could be her love interest. He might be intrigued by her unique existence and wants to help her adapt to the world. He could fall in love with her while trying to understand her physiology and emotions.
The Cheshire Cat could be a potential love interest. His mysterious nature and ability to disappear and reappear could be alluring to Alice. He could guide Alice not just through Wonderland but also into the depths of a relationship, using his wisdom and his rather unique charm.
A fellow shaman who has a similar power level and shares his determination to fight against the dark forces could be a potential love interest. For example, someone who also has a deep connection to the spirit world and can understand Lyserg's often - times single - minded focus on his shaman duties.