Megaman beating MK doesn't surprise me, pellets function like a constant trickle of slower needles. He is also good at knocking someone away when they get in with nair and jab buster hitboxes, which is done safely while shooting the pellets. His bair is actually better A2A than shiek's fair, with the exception that is suuuucks landing compared to fair. He is heavy, so MK has to win neutral a few more times before he can even win off a dash attack. Even if you are in the golden range, playing with your back to the ledge isn't so scary when you have a full arsenal of projectiles to pelt him with. Sticking him with a crash bomb means you can start to pressure safely and leave the corner, metal blade setups can kill MK very early...
Really it just comes down to Megaman has a great neutral, and it works in ways that hurt MK. He isn't supremely light like Rosa, so MK has a harder time making up the disadvantage. MK's slower speed in the air means it is easy to pick at him with bair, or outright kill/ do 40% with tornado juggles. The saving grace for MK, in my opinion, is gimping. Megaman doesn't recover extremely safely, BUT he recovers a lot with each hit of MK's dair, so it won't outright kill him but it will rack up a lot of damage.
Megaman's huge hands also can stuff MK in close range footsie situations, and a pivot grab can stop a dashing approach pretty cold. Its a tough situation, where MK is sitting there taking pellets, a standing shield can get you grabbed, thrown back into a distance, and repelleted and everything else has an answer for MK. This type of zoning struggles against burst hitboxes, movement, and needles, none of which MK has that beat needles. Its a MU I don't fear coming across in bracket too much, especially since there are more 'lets learn the death combo against top tiers' than fleshed out neutral MKs.
@Shady Shaymin There is also the issue of risk/reward. I'll use ZSS as an example, as megaman has really different gameplay. Landing a tilt
can open up some situations where huge punishment happens, like knocking them back and then running up with a grab, but landing a nair or uair
will open them up to harder punishment. Usually, an aerial has a better reward than a tilt, with notable exceptions across the cast such as DK utilt, MK as a character, etc. This is not only due to the nature of the moves, but the fact you can be moving towards someone when you hit an aerial. Additionally, if you hit an aerial and land the next frame, aerials usually have better recovery data for the power.
Also, missing a tilt barely and getting smashed blows, and a retreating an aerial often doesn't have this risk, again except against particularly good smashes.
that all said, I have been working on a more grounded, footsies/neutral focused ZSS, with some decent results. we see that the aerial only ZSS is open to a lot of problems, so im hoping my progression is one that will naturally flow with players getting better. Not to say im some sort of smashsayer, but often I think things in theory, try them with limited success, then see a top player use it and im like 'yea, thats how it looked in my head". Im seeing a ZSS that abuses her superior range more frequently, as well as her
phenomenal walk speed and above average pivot data.
Moves like ZSS d-smash are interesting and relevant as well, where a SH aerial is the best way to pass over the hitbox. Many characters contort themselves in ways that make them harder to hit when airborne. finally, aerial focused gameplay is a traditional thing in smash, it has taken some players a while to get used to how powerful a grounded character can be in sm4sh, even if its not melee falco/fox facing away utilt unbreakable =P
Re: Falco shine knocking you down. Can he follow up if I just roll away?
EDIT: holding my metal blade is in no way scary. I have access to pellets, crash bomber, leaf shield, and all my normal moves. You have no quick access to your normals. My pellets stop metal blade cold. Please, hold onto my metal blade all game. You aren't gonna win with MK's specials.