i think luigi's matchups are greatly misunderstood. along with his recovery. which in turn makes him underrated.
it isnt until you get luigi so far away from the level....that he relies on his up b sweet spot....that he has a bad recovery. and that isnt until very high percentage. and even then...you can pull some tricks off. id say sheik, falcon, marth, falco, zelda, pika, pichu, ness, and game and watch ALL have recoveries that are easier to edge gaurd than luigi's. a very underestimated recovery. i think its biggest down fall, is that if your opponent actually gets hit by your side b.....you are pretty screwed. but id be willing to say that nobody thinks of doing this (except me
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luigi does well on sheik, fox, falco, and marth. people who say otherwise honestly dont know how to play againt the characters properly, or simply never get to play agaisnt those characters. sheik and falco are possibly the worst of the 4 because they have the best levels to utilize agaisnt luigi. Characters like ganon, jiggs, zelda, samus, and peach pose some larger problems because thay can not be combod nearly as well as the 4 top characters. (cept peach can be combod fairly well, its her priority and recovery that become a problem)
Jiggs can use spacing with back airs to literally make it impossible to be reached. and can bait luigi into wavedashing into an f smash very esily. Ganondorf has great range, power to make luigi's recovery non existant, and he is a pain in the *** to edge gaurd. Zelda can not be combod, out ranges luigi with fair/dair plus luigi will wavedash into her powerfull moves a lot since she is not really fast enough to do anything except jump and do a move. samus has a rigged sex kick, doesnt get combod, and edge gaurds luigi better than almost any other character, PLUS she out survives luigi. and peach is close to even but can really give luigi problems because her priority is better than his. something that is pretty rare. i also find crouch canceling to be a pain for luigi.
sheik can be rediculously combod, and all she can resort to is needle camping and grab whoring. this makes her game one dimensional and vbery predictable, giving you an advantage. up throw and down throw can lead to down airs and chops. up tilt is great on sheik. and you can force her to recover on the stage for major punishent.....OR wavedash back and bair her before she ups b. recovering can be a pain agaisnt luigi.
with luigis sheild in hevay use agaisnt marth, all he can truely count on is grabbing luigi (which can be side stepped and cause A LOT of toruble for marth). the thing is....when marth grabs luigi there is very little that cant be DI'd out of. All marth really has is his difficulty to be combod in the air, and pretty **** good edge gaurding on luigi. but his range is canceled out by luigi's ability to wavedash out of a shield, and wavetilt super fast. plus luigi has great combos out of down throws and very good edge ghaurding on marth because of the wavedash edge hog, light shield edgehog, and back airs.
fox and falco can be combo'd better than any other character by luigi. and they are started with close to 6 different moves from luigi. they still do well however because of Fox's great verticle KO and shine. and falco has the lasers and rigged priority with dair. these are more of 50-50 maches that IMO have a small advantage for luigi because of the better combo ability. a very level dependent pair of matchups.
IMO the top tier troubles luigi faces are far less significant than the annoyingness and lack of options luigi faces with the other characters i listed.