Just from my experience and from what I heard, watched and understood about the match-up, so if there are any objections or any other points anyone wants to raise, feel free to post
Well, in this match-up, you're suppose to use your disjoints and range against Mario, since Mario's overall range on his moves isn't all that impressive (to put it lightly). Mix up your spacing tools between SHFF f-air, n-air, b-air, and d-tilt. Try not to jump
too much because if you're too predictable with your aerials, most competent Mario mains would just adapt, dash to you while you're in mid-air to close the distance and (attempt to) punish your landing and we all know that Corrin's landing options are (not bad but) lacking. The main advantages Mario has is in this MU is that once he manages to land his combo starters, you're gonna take a lot of damage, but he still needs to get through your wall
Mario's approaches such as grab, b-air and d-air are not that hard to deal with. N-air gets annoying though only because the only reliable way you can actually deal with it is by using f-air, b-air (although it's frame 13 so) or IP, but the thing is you can't really get that much out of retreating f-air or b-air. There isn't really any potential string you can net from landing the moves from that certain scenario or position so you're gonna have to settle for the low damage output. Regarding IP, just don't use it too much. Like, IP is really good. Don't get me wrong, but it gets predictable and most players might just shield it the next time they anticipate you using it. Shielding is kinda not that helpful because Mario's n-air barely has any end lag so it's hard to punish. I
think maybe a reverse u-air could work against Mario's n-air approaches. Like, the latter hitbox of u-air could beat out Mario's n-air and you can even get some follow ups out of it. Not sure about this one, just thought of it now. Lol. (
Edit 2: Just saw the new heat map for Corrin's grounded moves. U-tilt seems to do a fair job in stuffing Mario's n-air based from what I saw. I guess) Use your jab or d-tilt (both are frame 5 and are your fastest options on the ground) against Mario when they're trying to grab you. If you don't feel comfortable using both those moves, then a retreating f-air or n-air will work, or just run away and IP. Other than jab and IP, pivot grabbing should also be another option to take note of. In case they start dash > shielding to deal with jab/aerials/IP, use your pivot grab. You don't get much out of throws (other than positional advantage), it's your best option against an opponent that's trying to dash > shield. Well to be honest, I still think you can actually deal with dash > shield by spacing your aerials properly (use those retreating aerials) but grabbing is your safest bet against shield
Regarding DFS, uh. Y'know, having a projectile is great and all but Mario has a reflector so be careful. Don't be predictable with it. In fact, you should refrain from DFS in the neutral frequently. Just to play it safe. Use it though for tech chasing when you can or use it off from a n-air or f-air. Just don't throw it out that often. Dragon lunge.... yeah. No. Not repeating myself for this one. Counter surge, well, it's a counter so use it if you're confident that you can predict what your opponent's next move is. I'm not sure if you can counter out of Mario's d-throw combos
When it comes to combo'ing Mario, well, try not to overdo it because he could n-air out of Corrin's strings. Just go for the true combos or maybe start a string on him then maybe see how the Mario player reacts. If he's the type that jumps out to escape combos, that's a queue for you to punish their landing. If they're the type that n-airs out almost all the time. Just bait out the n-air then punish them for throwing it out. If they're the type that air dodges, well, punish it
I'd love to talk about perfect pivoting and how it really helps in the MU but eeeh. Don't think a lot of people have grinded or practiced PP'ing yet (correct me if I'm wrong) so I'll refrain from talking about it
Here are some video footages of the match-up. Some of these may be outdated (maybe only the first video) but it's all I can scrounge for in the archives:
