>>35477324Right/Justice VS Wrong/Injustice - A good Pokemon that tries to persevere all life VS an actual evil Pokemon that wants to destroy humans in order for Pokemon to take over.
Hot VS Cold - Something like R/S, 1 story with 2 different themes, one involving a team wanting to scorch the land and destroy the world to create a new one from the ashes and the other wanting to freeze the world to destroy it to start again.
Light - Dark - Necrozma kinda takes this spot, they could've had it be a counterpart to another pokemon, one stealing light that makes the world dark (eternal night) other taking the darkness and making the world light (eternal day), the 3rd legend would be a balance between them (so the normal 12 hour cycle)
Nature VS Technology - Pretty obvious with this one, preserving nature over building cities.
Evolution - Something I thought would make a cool game, have the theory of the meteor wiping out the dinosaurs be the theme, instead, it was 2 legendary Pokemon that did it by fighting (They wiped out the fossil Pokemon) which was the event that pathed way for humans to evolve and be the dominant species, the legends could be fossils that get revived by someone to try and re-create that fight to wipe out humans for something new to become the dominate species.