still having trouble facing little mac as a rosalina,
what are the best viable options for her again him
i already read the match up thread.
For me, the main thing is to make the middle of the stage your home, as Little Mac is much more vulnerable when backed near the sides.
Other than that, I tend to play more patiently against Little Mac, as a good Little Mac will ALSO play patiently (the common misconception is that he is rushdown and aggression like Captain Falcon, but he actually should be played more defensively and patiently, he's much more effective that way). Due to his super armour on so many moves though, you want to try not to pull the first punch as he can easily barrel through that. You want to bait him into making moves and retaliate, pressuring him off-stage and keeping him in the air. Even when chasing him in the air, always hesitate when following up unless you know he is in hitstun, as he can use his counter. If you hesitate to actually attack when you get near him, he is likely to end up using the counter but then you can just get him after the active frames of the animation. Using Luma to activate the counter while keeping Rosalina out of it's way is also a really effective strategy, as you can effectively counter his counter that way. It can easily bring him to the side of the stage if he is already in the center.
Shielding and grabbing is also your best friend against him, since grabs easily get him off stage.
Also while knocking him off the stage is the obvious option, don't shy away from top blast zone KOs if you get the chance, since he is just as easy to juggle as he is to pressure off-stage.
When he's off-stage you have an extremely clear advantage so you shouldn't have too much trouble. Just watch out for his counter once again, Little Mac relies on it to get safely back to the stage. It's easy to deal with though. Once again, just bait the animation. In most instances you won't even need to hit him after that, as he will have fallen too low to recover.
I don't find this a problematic match-up in the slightest anymore, it's one of the easier ones, but I admittedly had a bit of trouble with it when the game first came out. That super armour can be annoying before you figure out how to get around it.
Dunno if that helps, but it's what springs to mind. Maybe if you can mention what you have the most trouble with?