>>53891959Eggman is very crafty and would probably come up with some complex strategy using the moves/abilities he was given in his new form to amass resources and influence as fast as he could. If he was a Psychic type that would be worst-case scenario, telekinesis would severely increase his productivity and potential access to moves like Hypnosis would be an absolute game changer.
If he ends up on the RT continent (or anywhere else with technological human ruins) he would very quickly use whatever he could salvage to produce more modern technology and it would snowball from there, eventually he'd have an eggman empire just like in the games except now he could also 1v1 you without any tech necessary.
Don't even get me started on if he manages to find a legendary artifact or strike a deal with a less ethical legend/mythical like Darkrai...
The best chance at stopping him would be early on, maybe if he finds the Black Stone and tries to harness Zekrom without knowing the legend, he'll awaken it and it'll zap him to the extreme for having an impure heart before he has the means to stop it. If you got isekai'd as a technologically-oriented Pokémon such as Rotom or Porygon you'd probably be able to wreak havoc on whatever he's built for himself at that point, but that really just highlights the REAL danger of Eggman: He'd just change the entire genre of the setting and replace the pre-medieval fantasy comfiness with a bizarre futuristic theme park full of icons of himself. It'd be like a weird reboot of that old sonic cartoon with the animal characters living in his dystopia, and only vaguely resemble the original idyllic Pokémon world. Would you even want to save it at that point? Maybe his real plan is killing the vibe so the hero just throws their hands in the air and gives up altogether. Really showing off his 300IQ...