Pac Man's worst matchup so far seems to be either Rosalina or Lucario. Yoshi has an advantage, but Rosalina and Lucario's advantage vs Pac-Man seems stronger.
Both Rosalina and Lucario are impossible to gimp. At "ideal Fair offstage combo" of 80% or so, Lucario's aura intensifies significantly, and his up-B seems to allow him to recover off of damn near everything. (fair->fair-> toadstool jump, an off-stage combo that seems to kill the majority of the cast, fails to kill Lucario).
Beyond 80%, Lucario's hitboxes get better and better. Pac-Man has an easy time getting Lucario up in damage, but at high damages, the huge hitboxes and power behind Lucario clearly gives Pac-Man trouble. Lucario can bait Pac-Man's smash attacks with his down-B, and Lucario's reversal at 100%ish is a solid killing move.
KOing Lucario at 100% requires the use of risky moves (Smash attacks in paticular). Lucario is solid however at this percentage, and his own smash attacks, tilts, and aerials will punish your missed smashes and grab attempts. However, failing to KO Lucario "early" means fighting him at 150%+ (where safer attacks like Bair, or Melon will KO). By this point, Lucario's aura turns him into an absolute monster, his UP-B allows him to land anywhere on the stage (he can be offscreen-left, and his up-B goes so far that he can land on the right-side of a stage)
B-Spam cancels out most fruit one-on-one, and Lucario can throw out more mini-aura spheres than you can throw out fruit.
I think "managing" Lucario's % and relying on Bell near 100% is the best way to KO Lucario. Pac-man often times plays defense till the opponent is 150% and then delivers a killing blow, but this is not a good strategy vs Lucario.
You will not have any issues getting Lucario to 80%. His hitboxes are clearly weaker than Pac-Man's at low percentages, and dumb rushdown seems to work. Landing that final blow however becomes a pain.
Also, **** Lucario's "step back" when he smash attacks. So many times do I die because I miss my fair as Lucario stakes a slight step back before his smash attack. :-(
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Rosalina also fails to be gimped by most of Pac-Man's offstage fair-fair combos. This cuts off an easy KO option at 80%.
Rosalina is super-tall, so short-hop Fair -> DI back is an excellent "poke" against Rosalina. (DI back just in case she sidesteps / shields, which means she can't grab punish or tilt-punish you if you keep the distance appropriate). Most characters are too short for this poke option, but keep this matchup specific poke in mind. (On the ground, Bowser, Gannondorf, Rob, and Rosalina can be poked with Fair somewhat safely). As always, mix up your approaches.
But yeah, Luma blocks out most fruit spam with no effort on Rosalina's part. With "effort", Rosalina can use down-B to protect Luma and then catch fruit you've thrown at her. Her Down-B negates Hydrant as a projectile and also negates it when it is still on the ground.
Grabs vs Rosalina need to be executed immediately. Do not pummel with Luma nearby. Pummelling leads to a free smash attack from Luma. Its important to remember that Luma cannot roll or sidestep. Every thrown projectile or attack will typically hit Luma. It seems like striking Luma causes "hitstop": both Luma and Pac-man are momentarily stunned by the attack, but Rosalina can punish you during "hitstop".
The key seems to be separating Rosalina and Luma using the Hydrant, and playing a solid rushdown game when you know it is safe to approach. Running in on Rosalina's netural B, and short-hopping over Luma when Rosalina throws it is a way to get "in". Rosalina doesn't have any very quick attacks, so she is easy to combo. But her aerials in general have great range and priority, making it very difficult for Pacman to play a rushdown game against her.
So zoning with fruit doesn't work. Using fruit to cover a rushdown also doesn't work (it hits Luma and then Rosalina punishes your approach with her superior range). Hydrant zoning doesn't seem to work. Approaching with aid of the Hydrant is... okay... but gets predictable over time. Gimping at low percentages doesn't work because wtf. Rosalina's up-B is ridiculous.
So like the Lucario matchup, it seems to me like Rosalina tends to rack up a lot of damage before she dies.
I feel powerful against quite a lot of characters actually. Having played a lot of C.Fals, Little Macs, Bowsers and Ganondorfs, I have not had too many losses as Pac.
IMO:
Pacman is 60:40 against Little Mac. Start the match, place an Up-B trampoline in front of you, and start spamming Little-Mac with fruit. Watch him cry. If Little-Mac catches you out of trampoline positing, the matchup becomes a bit harder, so I'm not going to give Pacman any more than a 60:40 advantage vs Little Mac.
Don't underestimate Little Mac's aerials. They're bad overall, but they have decent hitboxes, and give just enough stun to often lead into a ground combo or even ground smash attack. Fight Little Mac _high_ in the air, and force him there with the Trampoline.
Outside of grounded side-B approaches over the Trampoline, Little Mac can be forced to approach Pac Man in the air. Up-B completely neuters Little-Mac's gameplan.
Pacman is like 60:40 against Captain Falcon. Pacman's forward-Tilt beats out
literally everything except C.Falcon's side-B (which can be side-stepped and punished). Its a slightly tricky matchup, because a Fair-Fair combo at the wrong percentage (ie: 30% or so) results in Pacman getting knee'd in the face. But overall, it seems that fruit + forward tilt beat out C.Falcon's ground game entirely... and forces him to use side-B on his ground approaches. (To be fair, that sideB KOs you rather early, but it is a hugely punishable attack)
Bowser and Gannondorf hit freaking hard, but Pac-Man just outzones Bowser. Pac-Man probably has 70:30 against Bowser, cause Bowser just doesn't seem to have a response to fruit spam. His approach options are terrible and predictable. Pacman gets the matchup-specific shorthop fair approach option. I rarely feel like I've been outplayed by Bowser... instead it seems like Bowser capitalizes on my mistakes. Pac-man "controls" the match.
Gannondorf is super-gimpable, although trying to gimp him is dangerous due to his side-B. If you get ahead on stock, this matchup feels like 70:30 (too dangerous for Gannondorf to side-B double-suicide)... although I guess its maybe 50:50 or 60:40 (Pacman favor) if Gannondorf has the lead. As long as Gannondorf has Side-B off-stage mindgames, its a tricky matchup.
Like Bowser, Gannondorf has issues against Fruit Spam. But he seems to KO Pac-Man with just 3 attacks or so.
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Hard Matchups:
Rosalina / Luma: 70:30
Lucario: 70:30
Yoshi: 65:35
Mario: 60:40
Ness: 55:45
I'm probably going to have to find better players before 100% being sure about the "easy" matchups. But it does seem like Bowser, and Gannondorf have to work very hard against fruit spam... and Little Mac doesn't really have a response to UP-B.