Such sound logic... (referring to unknown's post)
So what happens when you come at him with a nair and you hit his sheild. What can he possibly do to you before you get away?
Well, he could jump away and Fair. I mean, Pichu probably don't get hit because he can dash away but he's once again back and square one and in no position to keep the pressure on.
How is Marth going to get his kills? Random tippers?
No, he's going to grab Pichu and throw Pichu. And keep following Pichu until he reaches the edge. F-smash. Then he'll edgeguard.
On that note, Pichu's abysmal tech rolls make him one of the easiest characters to regrab or force into positions where he has to take an F-smash, Fair, or similar move so if he refuses to go to the edge you can very easily just build percent until your F-smash will knock him off or he's in killing range for U-tilt.
He can also U-tilt Pichu out of any aerial approach at like 95 (or during edgeguarding if he tries to go above him) and kill him outright. Considering the low risk in doing so and the relatively low percent he needs Pichu at to kill him with it, this is a pretty good option.
At least Pichu can reliably edgeguard (just get underneath or above with your first jump and nair.) Marth's dair and uair are a little too laggy to be chancing perfect timing with while offstage.
Side B > Pichu moves if you time it.
Fair > Pichu moves.
You can fast fall Fair and still get the ledge if Pichu's willing to go offstage. And it's pretty safe, provided you've saved your double jump, float Side B, or you're close enough to recover after Fair's lag (which is pretty common).
Not saying its easy. Marth does a lot of damage when he lands a comboing move, but Pichu has the tools to deal intuitively with everything Marth can throw at him. It's not impossible.
Marth dash dances or spaces Fair.
If the Marth approaches with swordy aerials that get shielded, he can get naired in the face.
This is false.
You aren't going to reasonably be hitting Pichu out of his nair with anything except your own nair and retreating fair, and maybe tilts. None of those have any real followup at most percents.
Jab, Side B, crouch cancel grab (situational percent and if they're not going behind you), and dash dance grab.
Grab has follows at most percents. U-tilt can kill outright, so it doesn't typically need a follow. Fair can often combo into more Fair or Uair if Pichu's not over 50 (or similar).
Jab doesn't follow the the flipside is that it's very fast and very safe and will still eat Pichu's Nair.
Dash dance into the first hit of Side B often can combo into U-tilt, which is useful at high percents (100+) for killing Pichu. This was, in ancient times, often used against Puffs and Peaches for killing them.