The ratio's aren't for description, they are just so you know how much of an advantage or disadvantage Marth is at. If you want descriptions then you need only ask.
I already talked about Pikachu, which is a pretty straight forward match IMO. I'll talk about Dedede in a second.
You asked how Marth deals with projectiles overall so I will answer. Honestly his method will change depending on who he is facing. In general though the only reason Marth doesn't have advantage on projectile campers is because they CAN camp.
Overall Marth has the best moveset and he has no bad moves. Jab won't see much use, but it's very fast and the only reason it isn't used is because Dancing Blade is just as fast and combos into itself.
When dealing with arrows Marth can swat them or SH over them.
When dealing with lasers Marth will want to roll, full jump, short hop, and instant double jump.
When dealing with bombs and turnips you can just catch them easily or dodge. You can swat turnips as well.
Marth can easily jab aura sphere's that aren't charged up.
Grenades can be shielded or thrown back.
Boomerangs can be jabbed.
PK fire can be rolled past or jumped over.
Din's fire is beaten with SH airdodges pretty easily.
Gyro can be shielded or used against ROB.
Laser is tougher to deal with. This is mostly about prediction, but you really can't stop ROB from getting hits in with this. Mostly Marth just has to stay slippery and evasive and in ROB's face.
Waddle Dees can be swatted away or SHed over.
Fireballs can be jabbed.
Thunder Jolt can be jabbed as well.
Needles can be SHed over.
There is an optimal way to deal with all projectiles and Marth doesn't have too much trouble dealing with any projectile. Also don't think you have to limit yourself to the one or two methods I listed for each projectile. Mess around with your options and see what works.
Now I'll talk about Dedede and alot of Marth players will probably rejoice over this and alot of Dedede players will give me hell for this.
From what I can tell after some more experimenting and more testing I think Dedede vs Marth is 50/50 even.
Now here me out. Most of you will say that Dedede has a CG , and outranges Marth, and can get grabs off anything Marth can do, and can waddle dee spam him.
So let me clarify a few things. Dedede only outranges Marth with F-tilt. That's one move. It's a decent move, but not that great. Good range, but the damage is a little low at 9%. Marth can SH over this and since Marth uses SH's as his main form of approach he will end up avoiding this alot. All the rest of Marth's moves outrange Dedede's other moves. And Waddle Dee spam is easy to deal with. They can be swatted and SHed over.
At close range Marth has plenty of good options to rely on as always and he still has his range. Dedede won't use f-tilt at close range since it will put him at frame disadvantage on hit. So once Marth penetrates the f-tilts range and sets up his spacing game then he is golden. Also Marth CAN gimp Dedede. Marth ahs some nasty tricks that he can do on Dedede when he tries to recover. First off he can just run off the stage and swipe at Dedede. Dedede can't do much since Marth's aerials are faster. He can airdodge and then jump again, but this is good for Marth since it makes Dedede waste jumps. If Marth is hanging on the ledge while Dedede tries to go over him to the stage, then he is set-up for an easy spike.
The real fun begins when Dedede uses his up b. If he aims for the stage then Marth can counter. Even if Dedede cancels his up b Marth will recover sooner then him as long as he countered a bit early and then Marth can just hit Dedede back out for more edgeguarding or repeat the scenario. If Dedede cancels his up b too close to the ground he will bust his *** giving Marth ample time to tipper f-smash in which case he will die if his damage is high enough. At the very least Marth has now reset the scenario. And of course if Dedede lands on Marth while he is countering then Marth will just knock him back out. If Dedede goes for the ledge he has to cancel his up b acertain distance above the ledge so he won't miss it. So if you for it you can hit Dedede back out if he tries to aim for the ledge, since he is vulnerable before he grabs it.
With this method Marth can inflict heavy damage on Dedede and make it extremely difficult for Dedede to recover. Now Dedede CAN recover. It's not impossible from what I have seen. Mostly he just has to be tricky and try not to get too preditcable, but the situation is heavily in Marth's favor and Dedede will usallly eat some hits before he can make it back. One way he can get out is if he hits the part of Marth's body with his up b that is facing away from the ledge this way Marth knocks him towards the stage when he counters. Dedede will eat some damage, but at least he ended Marth's recovery trap. Although Marth can counter this by not counter at all and just doing SH airdodge and then getting Dedede off the stage witha smash. But as I said this situation IS in Marth's favor so Dedede must be very careful.
Overall the main things that make it even are Dedede's CG, his camping while not extremely effective does help him out a bit, he is heavy so he doesnt die easily, and he has good recovery. But his problems are that his kill moves aren't good at all. They are all slow, so he cant really kill well at all. He has to rely on gimping with his aerials and his aerials aren't even that good either. Bair is good, but the rest are only above average. He has good close range options, besides his grabs, but none that are amazing and Marth outranges them all. Although his jab combo is good, but again Marth won't get hit by it consistently due to his spacing. Also a small tidbit on the CG. It seems like alot of Marth s have been saiyng that you can up b out of the shield grab. I have done it in tourney, but I don't know if it can be done consistently or if it's just because Marth flys far back from the d-throw. IF it turns out that Dedede can't consistently CG Marth then it's his advantage 60/40 no question.
I'll do the Snake match-up later.
WHOMG MARTH HAS TEH LIEK NO BAD MATCH-UPS?!?!? WTFHAX!!!
Yeah.
And niether do Falco, Snake, Toon Link and Wolf IMO.
Top tiers generally have no bad match-ups or 1 bad match-up. 2 at the most.
If you don't understnad that then you need to play some other fighting games.
