Mewtwo doesn't lose to GnW lol, we finally have proof to end that. It's even at worst, probably slightly in Mewtwo's favor.
You say you have proof, why don´t you post it?
I kinda agree though. These matchups work out on paper, but not quite so in practice. The main argument is the bucket, once filled you are one grab away from beeing 0-death. This doesn´t always work out that easy though.
Step one is getting the bucket filled. Now unless your enemy has no clue, they will be very careful not to do that. For example, Marios fireballs are pretty easy to bucket because they are slow and easy to react to. (The solution, don´t use fireballs) Projectile that can be charged though (Samus, Lucario, M2) are not only fast but also deceptive. Under a certain distance it´s impossible to bucket on reaction, and they will not risk shooting a long distance.
This forces you to try and read what they´ll do, they can use this to bait you. They also have a good amount of quick options out of charging. A wrong read will always get you punished because the bucket is laggy as hell, even a correct read will get you punished if you don´t get a full bucket because it´s still laggy as hell. (This is worth though)
Additionally, they can just not use it, or use it very rarely/only out of confirms. Overall I find it pretty hard to actually get a bucket.
Step two is deleting your enemies stock with the bucket. 0-death ez gg BUT WAIT: You have this insta-kill bucket of destruction, but your enemy is already at 70%+ (and 2 stocks). Do you REALLY want to use the bucket now? No, no you don´t. Optimally you finish this stock with an upsmash or similar, then 0-death with the bucket. But your enemy, now that the threat of you filling the bucket is gone, will camp like crazy to avoid the grab AND they now have an additional tool to work with because the bucket is full anyway. Of course you can always try to get a read with the bucket but the chance of wasting it... I´ve had buckets powershielded, it´s painful. A shieldbreak usually is also not worth it.
Last but not least, if you are at kill%, bucketing anything that doesn´t fill your bucket will likely result in death. I´ve had people try to bait it out when I was on one stock at kill%.
Now M2 can easily kill you with upthrow at above 100% (or backthrow or fair, or upsmash)
Samus can kill with nair or bair (charge shot also can kill pretty early out of some nasty confirms)
Lucario... this guy. It´s absurd how early he can kill, he got the bucket as passive on all his attacks. I think he still is probably the most manageable of the 3 though.
The bucket is overrated imo, because of the ridiculous power. Especially non G&W Players seem to think the bucket is some kind of magical free win button. Omg I can´t carelessly spam my **** projectiles because of the bucket, it´s so broken the MU is so bad buhuuu. Bull****! No doubt, the buckets presence is a major inconvenience, it´s nothing to take lightly, but also it´s nothing you couldn´t adapt to. How about you use the other like... 20 options that I cannot bucket? This is only this specific MU for you where it´s risky to use, while bucket is completely useless against 60-70% (or so) of the cast, not to mention the doubtful usefulness of judge. Game&Watch kinda reduces your option against him if he can... because he doesn´t have the options himself and he´s a jealous asshole.
TL;DR: I´d place M2, Lucario and Samus at an even matchup.
Cloud being -1?i would agree on that if edge guarding him wasn't so easy
His range, speed and killpower would easily put him at -2 if it weren´t for his lacking recovery. I think -1 is a good spot.