Well I was answering his question about how to deal with fair spamming:
this. Except ive been trying to watch how people get under marths fair, and the only thing ive managed to do is duck a wavedash under it while he does a rising fair (thats only if your lucky enuf for him to do a full hop or dj.) So what im asking is how to get past marths fair wall, since u cant beat it it seems.
As for dealing with fair to break out of combos, well, I don't think you'll ever get a true combo that's longer than 3 hits on marth. However, Luigi has a bunch of 2-3 hit combos on marth that do solid damage and put him in disadvantaged situations from where you can often get another hit. When he's knocked in the air and he has to land he's in a bit of a tough spot, as if he does a move and misses you can wd in and hit him, and you can also get under him to hit him with sh uairs and bairs sometimes.
As for the 2-3 hit combos, at various percents there's
dthrow -> regrab at 0
dthrow -> usmash
dthrow -> dsmash
dsmash -> utilt -> something
dsmash -> chop
dthrow -> chop
dthrow -> uair -> something
uthrow -> uair -> chop
bair -> waveland ftilt
uthrow -> bair -> nair at 0 (not sure if this one works, haven't tried it on humans, but it works on cpus of various levels)
full wd ftilt -> anything. If you go far enough on the wavedash it can combo into goofy stuff like usmash sometimes.
The combos involving uair are obviously DI dependent, but it's good to mix them in because it forces them to guess whether they should be survival or away DIing.