I found some mods for Shadow Mewtwo and Shadow the Hedgehog.
They're pretty well done for a fan work, though I think Shadow Mewtwo's moveset is slightly overtuned, even considering that his special moves make him take damage, and Shadow's has some odd attack concepts.
Shadow Mewtwo is actually pretty darn good conceptually. His attack changes cause him to exude...well, honestly the kind of power that base Mewtwo should. The only visual thing I don't like here is that his neutral aerial just straight up has worse particle effects, and up smash is harder to read. Psywave having dummy strong hitstun in exchange for taking damage is pretty cool, I just think it has too much knockback. Lucario is pretty light, but dying at 86% seems a bit much, and the extra knockback kinda defeats the purpose of making it more of a combo tool anyway.
Miracle Eye's effect is cooler than Disable's effect, but it seems to also be weaker since it doesn't actually shut down your opponent. I also kind of dislike how it wasn't changed to affect his other special moves like it does in Pokkén Tournament since that was kind of its sole purpose there. To be fair, I don't think it effects Psywave specifically, but I think it would have been better to make something up since Miracle Eye is kind of what makes Shadow Mewtwo so unique.
For Shadow, I think a lot of his attack concepts are either strange or not excecuted in a way that works super well. Most of the issues with his physical attacks are that they just need to be pushed farther; Have his slide kick shove those feet farther and such. I'm not super sold on his red energy attacks since I feel like Shadow is a more physical combattant with his chaos powers serving more to supliment/enable his attacks rather than
be his attacks. Also, his down air looks like an up air at the start. It is really cool though, and is definitely something that players could get used to.
His special moves are really cool, but there's too much contextual stuff going on without much apparant reason. His up and down specials are both teleports for some reason, but his down special turns into a dive kick while in the air. His side special acts completely differently whether you charge it or not, and can't be charged in the air and instead looks like the grounded charged version, but acts like Onslaught? I'm into all these attacks individually, but all together they don't make sense.
All in all, I really like this implimentation of Shadow Mewtwo, and I'd be so down for something like this as a clone, or with less normal attack changes, an Echo Fighter. The Shadow design is a great showcase of just how different Shadow could be from Sonic, and while the special moves need to be workshopped a bit, I think they nailed his style and personality, with most of my other complaints being kinda nitpicky.