Definitely not. In the Transformers universe, Optimus Prime represents leadership, honor, and protection. Associating him with a child in an improper way in fanfiction is wrong. Fan creations should promote positive values. We can have fanfiction where Optimus Prime is a mentor or protector of children in a proper, non - inappropriate way, but not the other way around.
A simple fanfiction could be that Cade Yeager discovers a hidden ability within Optimus Prime that no one else knew about. This ability helps them defeat a powerful enemy that was about to destroy the Autobot base on Earth.
In some fanfictions, Soundwave might be malfunctioning and Optimus tries to help him. This creates a unique situation as they have to put aside their differences. Their interaction could show a different side of their characters, like Soundwave's vulnerability and Optimus' compassion outside of the normal Autobot - Decepticon conflict.
One plot could be that they are on a mission in an unknown planet. They get lost and have to find their way back. During this time, they rely on each other's skills and start to understand each other on a deeper level. The lemon part could be the trust they build which is like a warm, fuzzy feeling in their relationship. For example, Bumblebee might find a way to communicate better with Optimus Prime during this tough time, and Optimus Prime in turn, protects Bumblebee more fiercely.
One common theme is adventure. They might go on missions together across Cybertron or other planets. Another theme is sacrifice, where either Optimus or the reader character might be put in a situation where they have to sacrifice something for the greater good.
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.
Optimus Prime is shown as extremely powerful in comics. His strength lies not just in his physical might but also in his leadership and determination. He can overcome seemingly impossible odds and lead his team to victory.
Optimus Prime is extremely powerful in the comics. His strength is shown through his ability to battle against powerful Decepticons and protect Earth. He has advanced weaponry and a never-give-up attitude that makes him a formidable character.