>>22812854I got ya covered Anon. There's a few different hacks that do this. There's Pokemon Gold Hard Mode found here:
http://www.romhacking.net/hacks/1632/There's also a few different crystal hacks out there. One of them that comes to mind is Crystal Enhanced Version. There's even a TVtropes page on that if you're curious. It's one of the more difficult ones I know of just from sheer level difference and Pokemon changes.
I would just link you to the Patch but the author seems to have made it impossible to get to, so here:
https://www.sendspace.com/file/wyh8e0One last one I can think of is Pokemon Crystal Kaizo if you're into that kind of stuff. I personally don't find it as hard as Crystal Enhanced but it's worth a shot to be entertaining right?
http://www.romhacking.net/hacks/2178/I assume you know how to get roms and patch them, if not just Google it.
I hope that helps your needs Anon.
