Griselda and Issei could make an interesting pairing. Their different personalities could create some fun and dynamic interactions. Issei's boldness and Griselda's more reserved nature could be a contrast that works well in a story.
Another good pairing could be Griselda and Rias. As two powerful female characters in the Highschool DxD universe, they could form a strong alliance. They could also have some friendly rivalries, like competing for the best strategies in battles or for the loyalty of other characters. Their relationship could be complex and full of interesting plot possibilities.
Asei the dragon could also be a good match. The OC Queen, with her own unique abilities, could interact with Asei in a way that explores the lore of dragons and devils in the Highschool DxD universe. They could embark on adventures together, with Asei's power and the Queen's intelligence making them a formidable duo.
Koneko and a god of nature could form a unique pairing. Koneko's connection to her cat - like instincts might be related to the god of nature's domain. The god could help Koneko further explore and enhance her powers, while Koneko could show the god a different perspective on the world of the supernatural that exists in the High School DxD universe.
Another common pairing is Sasuke and Akeno. Sasuke's brooding and powerful nature might attract Akeno, who is also quite powerful and has a bit of a mysterious side herself. They could bond over their shared power levels and a mutual understanding of what it means to be different from the norm in their respective worlds.
Well, perhaps a fanfiction where Griselda gets transported to a different dimension. In this new place, she has to adapt quickly and find a way back home. Along the way, she meets new allies and enemies. This would be a great way to explore her character in a different setting.
A rogue devil lord who has his own twisted sense of justice. He sees the current state of the devil world in Highschool DxD as weak and wants to reshape it according to his own ideals. The killer then becomes an obstacle in his path as he tries to carry out his plans, which often involve sacrificing the innocent. This antagonist would bring in a moral dilemma for the characters.
One potential pairing could be Naruto and Rias. Naruto's determination and strong will would pair well with Rias' leadership and powerful devil abilities. They could support each other in battles and in understanding the differences between their two worlds.
Blake Belladonna and Koneko Toujou. Both are strong female characters with a bit of a mysterious side. Blake's Faunus heritage and her experience with the White Fang could be something that Koneko, with her Nekomata powers, would be interested in. They could bond over their similarities and differences, and perhaps team up in battles against common foes.
Ruby and Issei would be an interesting pairing. Ruby's innocent yet determined nature combined with Issei's perverted but also heroic side could lead to some really fun and dynamic interactions. They could learn a lot from each other in terms of combat and dealing with different types of threats.
Ichigo and Akeno could also be an exciting pairing. Akeno has her own unique powers and a mysterious side. Ichigo's straightforwardness and strong moral code could contrast with Akeno's more complex nature. They could work together in battles, with Ichigo providing the brute force and Akeno using her strategic and powerful attacks.
Rex and Rias could be an interesting pairing. Rex's no - nonsense attitude and his power could be a good match for Rias's leadership and devil powers. They could learn from each other and face challenges together.