One idea could be a story where Godzilla and Indominus Rex are forced to team up against a common, even more powerful enemy. Maybe an alien invasion that threatens to destroy their world. They start off as enemies but gradually learn to work together.
The strength of Godzilla and Mothra in the manga is hard to determine. It depends on factors like the environment, their health, and the writer's creative direction. Sometimes Godzilla might overpower Mothra, while at other times Mothra could find a way to gain the upper hand.
A possible plot could be that Indominus Rex somehow gets teleported into Godzilla's world. Confused and angry, it starts attacking everything in sight. Godzilla, seeing this new threat, decides to take it on. Their battle could cause massive destruction, but in the end, they might reach a truce when they both realize there are bigger threats out there.
According to the plot, King Kong and Godzilla in the movie were rivals in love. They were both monsters controlled by humans, and there was no winner. However, in the novel "Global Familiars: The First Godzilla," the protagonist, Wang Cheng, had the soul of the Titan creature King Kong. With the addition of Godzilla's doppelganger, King Kong and Godzilla could perform well together. Therefore, it should be up to personal preference. Let me recommend the novels "Global Familiars: The First Godzilla" and "Starting from the King Kong Skeleton Island" to you. Both books are about all kinds of monsters colliding with each other. It's very exciting ~ I hope you like this fairy's recommendation. Muah ~😗
You could also develop its character based on its experiences with the environment. If it has to struggle to find food in a certain area of Jurassic Park, it might become more resourceful and determined. It could start to explore new areas and develop a sense of curiosity about its surroundings.
The relationship can be developed through mutual need. For example, if the human is lost in the dinosaur's territory, the T - Rex could initially see the human as prey but then realize the human has some unique skills, like making fire or using tools. This could lead to a truce. Or if the T - Rex is injured, the human could use their medical knowledge (assuming some sort of knowledge transfer in the story) to help the T - Rex, and in return, the T - Rex protects the human from other threats.