Squirtle:
Squirtle is actually just as mobile as Marth. He has similar aerial mobility values, and has that fantastic pivot with hydroplaning options that allow him to stay mobile on the ground. However, he loses to Marth because Marth outranges him, and because he gets punished harder for mistakes than he punishes. That said, because Squirtle is highly mobile, there is room to outplay Marth, so this matchup is not unwinnable.
Marth can force Squirtle to air release out of a grab, and has plenty of options once he does so. His most popular options are f-air, d-air, f-smash, u-smash and regrab. Grab release > d-air can be survived by good SDI so that the spike sends you into the stage floor instead of to your death. The other maneuver to be aware of is his usage of up-b. Due to the way Squirtle applies pressure, and the fact that Marth's grab is so deadly for Squirtle, Marth will be relying on his shield as a strong defensive option. Up-b OoS is invincible on frame 1, so be wary of being too eager to pressure his shield.
Playing Squirtle against Marth is all about finding ways to get inside, and maximizing your damage output once you do. Approaching via aerials tends to be unsafe due to shieldgrabbing and up-b OoS, although a rising b-air can be effective, especially at low percents when his up-b is unsafe on hit. Shellshifting/hydroplane f-tilt, mixed with short-hop-air-dodge jab, and empty short-hop grab can all be effective as well.
Once you get in, you need to be relentless without being careless. Always keep in mind that Marth has strong but high-risk gtfo options (frame 4 counter, frame 1 invincible up-b). When you go into this match, one of your early goals should be finding out how he uses up-b. If you can bait one early and punish it hard, you make it much easier to apply pressure later on in the game. There are two positions you want to be in to apply continued pressure. The first is below him. Squirtle is a fantastic juggler, as double jump u-air is lightning fast and can be done in reaction to an attempt to use side-b to stall. Use empty short-hops to gauge reactions, and punish with grabs/u-tilts/u-airs. Marth isn't great at dealing with Squirtle below him, as d-air has high cooldown, and stalling with side-b can only help so much. Stay lower to the ground so you don't overcommit to your juggle attempt though - you don't want to end up above Marth, as he is also a potent juggler. The other position is when you have Marth trapped on the ledge. Marth suffers heavily from RCO lag, although using f-air before he lands is still pretty safe. In any case, Marth still has a lot of trouble returning to the stage from the ledge against a waiting Squirtle. Stand outside of ledgehop f-air range, but don't try to challenge him on the ledge. Use f-air/f-tilt/jab combo/d-air/grabs to keep him off the ledge.
Camping Marth is also something that shouldn't be dismissed. If you notice that Marth is approaching you (which will likely happen if you have the lead and are already fatigued), don't be afraid to play defensively, because Squirtle can make it hard for Marth to approach as well. Be smart with Water Gun. Catching his f-air with a Water Gun creates a good opening for an approach. Otherwise, use it to mess with his spacing/zoning, which will diminish the effectiveness of his approach.
The Squirtle player really has to be the one dictating the flow of the match here. Make Marth feel uncomfortable, and don't let him get into that flow where he's shutting the match down, easily swatting away all of your approaches. Whether you fighting or staring each other down should be determined by you, and when you can do so, this matchup becomes winnable.
Ivysaur:
Contrary to Squirtle, Ivysaur can compete in the range department, but lacks severely in the mobility, which unfortunately equates to a much harder time against Marth.
Marth doesn't really have any Ivysaur-specific tricks that make this matchup difficult. Rather, it's just his basic moveset that gives Ivysaur trouble. D-tilt by the edge is particularly dangerous, but Ivysaur just has to be careful around the edge in general. It should be noted that Ivysaur can Bullet Seed out of the final hit of Dancing Blade if Marth uses the down-variation.
Ivysaur has a lot of difficulty dealing with the way Marth approaches. Confronting Marth from the air while facing him is out of the question, since Ivysaur's f-air is so slow. If going from the air, Ivysaur needs to be facing backwards, and Marth's dash speed combined with the range on his f-air (RAR b-air from Marth really hurts too) makes b-air less safe than it should be, when b-air does minimal damage in the first place. Approaching from the ground isn't much better, so Ivysaur shouldn't approach at all. B-air works when spaced perfectly if Marth is already in the air, and grounded up-b is great for sniping a Marth that gets too comfortable closing the distance. Ultimately, however, in order to keep Marth from getting past Ivysaur's defenses, the Ivysaur player needs to be outplaying the Marth player pretty hard. Once Marth does get in, Ivysaur has trouble getting Marth off, as Bullet Seed is extremely high risk, b-air hits in the wrong direction, and f-air is too slow. Marth also edgeguards Ivysaur extremely well. Overall, I would recommend switching Ivysaur out as soon as possible.
Charizard:
Charizard has an interesting matchup with Marth. They both have similar movement values, notably the very high dash speeds, yet the matchup is not all that dynamic, largely because Charizard should be focusing on completely controlling the pace of the match.
If Marth manages to get Charizard in a compromising position, between juggling, edgeguarding, and Charizard's general ability to avoid follow-ups due to his slower moves and large frame, Marth is going to be able to tack on a lot of damage. If you end up in the air above him, make sure you are thinking hard about when to use your jumps, as once you are stuck above him without jumps, it is virtually impossible to return to the ground. B-reversals may be able to give you enough of a momentum shift to get past the juggle, so always keep those in mind. Because of this, you want to shut the match down to a zoning game, and aim to deal damage gradually, but safely. Short bursts of Flamethrower can be effective, as can f-tilt. The overall goal is to slowly limit Marth's space, and push him towards the ledge.
However, this does not entail standing still and throwing out moves - Marth will outmaneuver you if you play that way. Instead, take advantage of Charizard's amazing movement. Move in and out of Marth's zone (use that dash speed; the closest you get should still be outside of his f-smash range). If he goes for an approach and you're not sure you can punish it, ride the dash away from him - depending on the situation, you can throw out a turnaround Flamethrower, a Rock Smash, or even do nothing and note his reaction to a failed approach. The tricky part is recognizing while doing this when Marth is open, and capitalizing. Most of the time this will come in the form of a dash grab or a dash > u-smash. If you manage to push Marth towards the ledge, these opportunities will present themselves more often.
Just as with Squirtle, juggling and ledgetrapping are strong tools for Charizard in this matchup. Charizard's juggling on Marth is not as effective as Squirtle's since he requires more commitment on his moves, but between u-smash, u-air and grab he can still do very well. Charizard does extremely well at ledgetrapping Marth though, between Flamethrower and grab. Conversely, returning from the ledge as Charizard against Marth is also very difficult. Ledgehop away, mid-air jump Flamethrower landing on stage is a strong option, as if Marth is standing far enough away to avoid the ledgehopped aerial, it's difficult for him to obtain a guaranteed punish on that. But of course, mix it up.
Switch Strategy:
Whether you start Squirtle or Charizard should depend on the stage. On cramped stages such as Lylat Cruise or Battlefield, you should definitely be maximizing your time with Squirtle. On stages such as Final Destination or Pokemon Stadium 1, which are more spacious and are worse for Squirtle's grab releases, you might consider starting Charizard.
The switch strategy I follow in this matchup is to use Ivysaur as little as possible. With the other two, play as outlined above until Marth is at kill percents, then switch for the kill.
Try to avoid the situation where Squirtle is at KO percents and Marth is at very low percents, especially on cramped stages. If Squirtle were to die, Ivysaur would not be able to get a switch off without leaving Charizard to take a hit, which on cramped stages could mean 70+%. I would strongly consider switching to Ivysaur as a sacrifice in such a situation.
Stages:
From a starter list of BF/FD/SV/PS1/CS/LC/YI, this would be my preferred order:
- Smashville
- Pokemon Stadium 1
- Castle Siege
- Battlefield
- Yoshi's Island
- Final Destination
- Lylat Cruise
So strikes would be from the bottom up.
Ban either Final Destination or Lylat Cruise. Maybe Brinstar since that stage does not favour Charizard at all.
My counterpicks would be Rainbow Cruise, then probably Smashville and Pokemon Stadium 1.
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Okay... I wrote a lot more than I expected to lol. I hope that helps, as I think Marth is one of my better matchups. Any comments or additional input would be great. I'm fairly confident in my Squirtle and Ivysaur evaluations... less sure about what I think about the Charizard-Marth matchup.