With all of the talk about
, I have some things to say about him and I want to state my current opinion of him in detail.
So, Luigi is a very hot and cold character. I think I heard him defined as that in Smash 4 but honestly, he really wasn't.
His recovery which is arguably one of his biggest weaknesses in Ultimate (and Melee as well) was actually very good in Smash 4 thanks to Cyclone which allowed him to both edgeguard for free and recovery without fear of being challenged. Luigi had hardly any trouble making his way back to the stage so which meant that being off stage was safe for him. Any character that can't be challenged off stage is not really a hot and cold character. However, in Ultimate, due to his nerfs to Cyclone, Luigi no longer can recover with no fear of being challenged which means that he is now much easier to edgeguard off stage. While in Smash 4, his recovery and edgeguarding were good enough to carry him from being a mid tier to a borderline top tier, he's not able to anymore in Ultimate which harms him a lot.
Speaking of nerfs, many of Luigi's best options were nerfed and the game mechanics hit Luigi in some areas as well. The combined nerfs to his recovery and the fact that edgeguarding is generally a better option than Smash 4 make his recovery significantly worse. Not Chrom, Little Mac, Captain Falcon, or Ganondorf level of bad, but still not that great. Another indirect nerf was the fact that Luigi's air speed was not increased to the same extent as the rest of the cast and his air speed, (despite still being second worst) is probably worse in comparison to the rest of the cast overall.
However, these major nerfs were a trade off for small buffs in many other areas of Luigi's kit. The most major buffs he received are as follows: Getting back his Smash 64 up-tilt which functions similar to Mario's Smash 4 up-tilt, the significant decrease on down tilt's end-lag, the buffs to his ground movement speed, back throw's increased knockback (it kills reliably near the ledge at 110% or below what were they thinking?), and the increased knockback to his down-b. Also, Luigi benefited from the ability to up-tilt out of a dash as well and his aerials having even less landing lag that his Smash 4 aerials (which already didn't have much landing lag) helps him to pressure characters a lot better.
Luigi also received a new grab but I'm going to keep it short and say it wasn't really a nerf or a buff, but a bit of a trade off.
Luigi has kept some of his strengths from Smash 4 being his down-throw, combo game, and fireball, all of which function pretty similarly to their Smash 4.
Luigi also keeps some of his weaknesses from Smash 4 however, because of the characters who are currently popular in competitive play and the changes to Ultimate's mechanics, these weaknesses are more problematic here than in Ultimate. These weaknesses are being out ranged, juggled, and camped. Luigi can deal with camping to some extent but the other two are the two things that can change a matchup for Luigi. If Richter and Simon were to only use their close ranged moves and not use their projectiles, Luigi would easily win. But because of their range and projectiles, they can put up a pretty good fight against Luigi.
Speaking of matchups, Luigi's top and high tier matchup spreads are honestly kind of wack. He loses hard against characters like
,
,
,
,
,
,
, and
but still possess the ability to do well against other characters like
,
,
,
, and
. However, when Luigi fights against another mid/low tier, he tends to do a lot better because most mid/low tiers can't really contest his frame data. There are a few exceptions of characters who can exploit Luigi's weaknesses like
,
,
,
, and
/
but he possesses the ability to do well against most of the other characters.
Tier wise, I'd say Luigi is probably a high mid tier with potential to go up or down depending on how favorably he is treated in the upcoming patches, and how well Luigi mains preform in the future.
I know this kind of turned into a long essay which wasn't what I intended, but I figured that I should try to touch on as much of the character as possible.