@ShinyLegendary
Thank you for the activity on this thread, and I am not being sarcastic. But you probably want to belay the posts that are blog-ish "I hate this MU, this one bothers me etc etc".
I am not trying to backseat moderate, but I want to explain. You may see similar posts from top players, but that is actually somewhat valuable meta information (though you could argue we let them get away with more than most, which would be fair). The fact that X top player thinks a MU is even, but HATES it, while likes struggling in a losing MU... can give us good insight on what ffrustrates top players. Think about this; if Zero can't find an answer to a certain sequence, the dude at your local won't for sure. Find things that disrupt top players...
This is an answer to your question as well! Watch some recent IcyMIst, ESAM as Samus,... sk8terjay maybe? Idk if hes still around. But watch sAmus matches, and see what kills her. What beats her in neutral. When can she use her combos, and when can you keep her away easily? How does she kill? When does she struggle to kill? How does your character kill her, is he risking a return kill in this situation, what is the chance you will win... etc etc. Really analyze the videos, don't just stare. This will take some practice at first but is the best way to get better in many instances.
Think about options. Don't look for 'Oh, ESAM chose wrong here and got hit', look for 'Oh, this option looks REALLY tough for Samus to even have an answer, even when ESAM knew it happened he had to do a lot to get around it'
PS Zair is incredibleballs and low key one of the best moves in the game. Gggrrrzap. IMO the Robin MU is losing, and to a lesser extent the same with mario, because of this AWSUM BIZZAPIN GUN.