In neutral you should be looking out for dash attack and dash grab. They are his main combo starters. He'll be looking for those from 0-30% since it's the main window for getting his ladder combo early on. He can also get them from up airs on the plat as well but it depends on where he is positioned and how many jumps he has burned.
Same idea applies when you are at 70-90% except he is looking for dash attack into up B.
You should try to play outside of his dash attack/dash grab burst range and not overextend in neutral.
If he is multijumping, he's generally looking for a landing nair combo starter. Up air/nair him depending on how close he is to you.
If MK gets a ladder to the side, you're pretty much fucked.
Dtilt is a strong poke that can lead into a tech chase dsmash or fsmash at mid-late percents. DI up to avoid being put in a tech chase situation.
Sometimes its okay to chuck out dsmash/usmash in neutral as a hard callout against his dash attack/grab.
Same idea applies if he is multi jumping above you.
Getting laddered sucks but you want to mix up your SDI and DI as hard as you can. You can start SDIng around the third up air since it becomes stale and easier to get out of. You can also mash up B too to get out and kill him off the top if he is next to you or escape in a position to where he can't Up B himself to kill you.
Your main goal when it comes to escaping ladders is to not escape the ladder but to avoid the finisher. The up airs themselves don't deal much percent but the finisher (depending on MK is positioned) have enough knockback to kill.
Outside of ladders, MK has formidable edgeguarding and ledgetrapping. MK will try to wall you with bair/fair if he is ledgetrapping.
His edgeguarding is really strong offstage but he will try to cut off low recoveries with nair or neutral B.
Don't recover high otherwise he will up B snipe you. But, don't be afraid to recover high. You can up B away early on to avoid getting punished and mix your recovery downwards.
Watch out for Fsmash at high percentages. It acts like our usmash and he'll use it as a hard callout if we overextend.
MK is really hard to edgeguard since he has multiple jumps and 4 different specials that all act as recovery options but up air cuts off high recoveries and forces him to recover low.
Always ban FD
Try to take him to Town or Kalos. The higher ceilings work against his ladder combos and we have more space to move around in.
Time out MK if you have to. Although he has multi jumps and many mobile special moves, we move faster in the air.