****it.
I was going to write a decent sized summary, like with Ike a while back, but I'm pretty tired after updating Oil Panic!
Some things you should maybe try:
Dash attack stage spikes MK a LOT when they do the shuttle loop near the edge. It bullies through the attack and hits him against the stage. I'm not sure if it has spiking potential on most stages, but it does work on Battlefield, and I wouldnt be surprised if it worked on Final Destination.
But yeah. The dash attack, aside from gimping, can slip up some people depending how they DI. If they actively hold back when hit, they're placed ahead of you for a second Dash. If they hold the other way or do nothing, they're placed behind you ready for another dash attack. This doesnt work too much after the first few times, as they expect it. I don't claim to be a high level player, but maybe this works there too.
Still on the subject, the dash attack, the dsmash, and the dair beats his Mach Whorenado. Dsmash is very nice for killing them, but realistically, it wont happen much. Mach Tornado is used for getting some damage on your opponent, so they try to avoid using it when you can react to it. Dash attack has worked for me, but the dair has some woogy timing.
Setting him up above you is a must in this battle. You cant do much sideways, except for perhaps Dtilt and Turtle, so you're going to be most effective under him. Nair his ***, UpB when you can, and Uair stall him at every point.
Uair is pretty sweet when they go for the glide attack. Poof poof them up as they make their steep descent, and they're up in the air again, IN FREE FALL. This means you can have your way with them.
Try to airdodge out of any momentum he gains on you, as you dont want to eat too many attacks, and Dair to avoid getting caught up above him. Don't be predictable, by any means, but also do what you must to get out.
You have a projectile which will force him to act. Neutral B? Hammers/Dash. Fly above? Now he's above you. Sweet. Roll? Dtilt, Ftilt, Grab, or smash. He might be fast enough to dash grab past you're food stuffs, but Im unsure. If so, then he's predictable here.
So yeah. Sorry I'm barely touching on some things. I just don't feel like going in depth about it all. Hopefully theres at least one thing I said that can help you.
Good Luck Hylian!