First, you need to understand Optimus Prime's character. He is a noble leader, so make sure his actions and decisions reflect that. For example, he would always put the safety of his team and the greater good first. Then, come up with an interesting plot. Maybe it could be about a new Decepticon threat or a journey to a mysterious planet. Also, include some great action scenes like epic battles between the Autobots and Decepticons.
One possible fanfiction could be about Sentinel Prime and Optimus Prime having to work together to save Cybertron from a new, powerful enemy. They might start off with some differences in their approaches but gradually learn to combine their strengths.
In a fanfic about Optimus Prime x Megatron, their relationship could be explored in a more philosophical way. For example, they might debate the nature of good and evil, power and responsibility. Optimus believes in protecting all life, while Megatron has his own ideas about power and how it should be used. This kind of fanfic could show how their different viewpoints could either bring them closer together or drive them further apart.
A great angle for a Megatron x Optimus Prime fanfic could be a body - swap situation. They are forced to inhabit each other's bodies due to some alien technology gone wrong. This leads to them having to understand each other's perspectives on a whole new level. They start to see the reasons behind their actions in the past and develop a new - found respect for one another.
Another theme could be about cooperation. They often team up to overcome challenges, whether it's a powerful enemy in both their worlds or some sort of natural disaster. In these fics, their combined skills and abilities are crucial. For instance, Ash's quick thinking and Optimus Prime's strength work together to save the day. Also, the theme of discovery is present as they learn about each other's worlds and cultures.
Well, it could be a fanfic that involves the character Optimus Prime in a zone called Shadowzone. Maybe it's about some adventures or challenges he faces there. Without reading it, it's hard to say exactly.
Optimus Prime could fit in as a powerful ally. He would be like a super - powered being in the RWBY world. His presence could shake up the power balance. Maybe he arrives through a portal and immediately starts helping the RWBY teams fight the Grimm. He could be seen as a symbol of hope, much like the Huntsmen and Huntresses are in RWBY.
Baby Optimus Prime's character can be developed by exploring his relationships. If he has a mentor figure among the Autobots, his interactions with that character can shape him. He might look up to this mentor and try to imitate their good qualities. His relationship with other baby Transformers or younglings can also be important. He could learn about sharing, cooperation, and friendship through these relationships. Additionally, his discovery of his own strength, both physical and mental, can be a key part of his development. For instance, when he first realizes he can lift a small object that others thought was too heavy for him, it gives him confidence.
The other characters in the Highschool DxD world would have a wide range of reactions. The angels might see Optimus as an unknown factor and be a bit suspicious. The fallen angels might try to manipulate the situation to their advantage. And the normal human students would be terrified at first. But as the story unfolds and they see Optimus Prime's noble actions, they could start to look up to him as a hero, much like how the Autobots are seen as heroes in their own universe.
One example could be when Optimus Prime is written to ignore a reader - insert character's valid suggestions in a battle plan. It shows disrespect for the character's intelligence and contribution.