Marth Vs. Fox McCloud
Fox is generally considered to be the overall best character in Melee. He has unmatched versatility of playstyle, high speed, an amazing punish game, and a practically unattainable skill cap. Depending on who you ask Marth may be the most difficult character among the top tiers for Fox to deal with. Due to how commonly Fox is played and how potentially dangerous he can be, you cannot afford to not know how to play against him. Basically If you aren't good against Fox, you aren't good at melee.
General Strategy and Mindset
It's easy to fall into the trap of unconciously attempting to "match" Fox's high speed. This often will lead to you making more mistakes and putting your attention in the wrong places. Your attention and focus should be on the Fox player. Both your thoughts and your playstyle should be completely deliberate. If you find yourself making movements or extending hitboxes without purpose then you're likely taking unnecessary risks. At least while practicing this matchup (as well as against other fast/technical characters) try to mentally emphasize the economy of motion. Don't be scared to play slower than you normally would if you begin to get overwhelmed.
Dealing with Lasers
Sometimes Fox will try to force you to approach by shooting lasers in place or while retreating. You should not let this cause you to over-extend and be punished. Make sure you use the time he spends shooting lasers to gain stage position. If you are close enough to him when he Short Hops you can punish him before or as he lands. Short-hop lasers are unsafe at a surprising distance. Unsafe lasers can be punished with options like a Boost Grab or even a Pivot Forward Smash. Bottom line is - don't take laser damage for free.
Fair, Grab, Dtilt, and Nair will form the basis of your neutral strategy. By Dash Dancing in and out of Fox's effective range (the range within which you can't react to his options) you can control the pace and spacing of the match. Control of space is key. Try to bait out his aerials, and punish them after dashing out of their range. A good way to do this is by using Dtilt deliberately too far away to land. Use Fair and Nair to to beat his short-hop aerials directly; use grabs and Dtilt to exert pressure; and sparingly use Fsmash or Pivot Fsmash in Neutral just to "Keep 'em Honest". Exert pressure and show unpredictability with your fast-fall timings and drift positionings of your aerials. You have a huge amount of potential mixups with your short-hop options alone. Here are some examples you shouldn't ignore: Instant or late timed aerials; Double aerials; Empty hop fast-fall grabs; Fair into waveland grab (or many other attacks); even rarely used techs like Toy Dashing have uses.
You should be extra careful not to overuse your shield against grounded Fox. His strongest punishes on Marth come from his grabs, which are usually followed by multiple Upairs. Try to get very good at wavedashing forwards and backwards out of your shield. When your shield is hit with an aerial, you need to be good at knowing whether or not it is succptible to being shield-grabbed safely. This takes experience to learn, but watch for aerials that are too high off the ground and/or improperly spaced.
Do not overuse, but also do not ignore using rolls. An example of a good situation to roll out of might be to buffer a roll towards fox during his Nair hitting your shield, which is extremely hard for him to punish on reaction. A common bad roll habit is to always roll towards the center of the stage when trying to escape being pressured at the ledge.
Platform Pressure and Tech Chasing
When Fox lands on a platform you can react to his tech options with primarily: Short-Hop Fast-Fall Upairs, Uptilt, and Fsmash. You can also Waveland down onto the platform and grab him, especially if you expect him to spotdodge or shield. A great way to pressure Fox when he's shielding on a platform is to use Nair. Nair covers platforms rather well, and is difficult to punish with a Shield Drop due to hitting twice. It also has the potential to shield-poke.
Upthrow Chain Grabs
Marth's Uthrow chaingrab vs. Fox is a large part of his devastating punish game. Particularly on stages like Final Destination where if done perfectly, can net you a kill off of a single grab, even from 0%. When you grab Fox and Uthrow him, there are three types of DI for you to react to: neutral DI, slight behind DI, and full away DI. If he DI's fully away in either direction, your followups are the exact same. The only difference being that you may have to turn around, or do a backdash instead of a forward dash. Here is how the chaingrab functions from 0% through ~45%:
- 0%-16%: If he DI's away you re-grab in place. Neutral-DI and Slight-DI can both be covered with pivot grabs
- 17%-30%: If he DI's away you have to dash before re-grabbing. Neutral DI and Slight DI can still both be covered with pivot grabs
- 30%-~44%: Away DI in front of you, as well as Slight DI behind can be covered by a standing Utilt. Away DI behind you and Neutral DI are covered by a turnaround Utilt
- ~45%+: If he DI's full away, just keep dashing and re-grabbing. Away DI behind you and Neutral DI are covered by a Utilts and short hop instant Uairs primarily.
Tips and Helpful Information
- Tip: At 0% the re-grab can be extremely difficult. An option to avoid this is to quickly Fthrow and dash re-grab before starting your Uthrows
- Tip: Generally speaking at ~45% and higher you want to be pushing your opponent towards the edge of the stage to set up an easier kill. Weak Fairs are good for this, because tipper Fairs will often send them too high for a direct followup if they are at higher percents
- Tip: All of your dash-grabs should be Jump Cancel Grabs, which gives you more leniency on your reaction speed
- Tip: If you manage to catch your opponents double jump, then you can chain Uairs alone up to ~100%
- Tip: At around 55% a tipper Fsmash can cover every possible option. Standing Fsmash in either direction will hit any away DI, and walking slightly in one direction and using Fsmash in the opposite direction will cover Neutral DI
- Tip: At higher percents you can end the combo early in many different ways. Here are some examples:
- Weak Uair into Fsmash
- Nair to send the opponent offstage, running attack sometimes will combo into this or a regrab
- Tipper fair -> Fast Fall -> Fsmash will sometimes connect
- Weak Uair -> Utilt can set up a Dair Spike
- It is sometimes better to end your combos with reverse Upb when offstage
There are far too many of setups and mixups to memorize. Experimentation and practice are the best way to get a feel for what's best to use in a given situation. As a final note, chaingrabs aren't only useful on Final Destination. You can often get quite a lot of damage off of recognizing when re-grabs are possible on any stage, especially when you get a grab without a platform above you, or when on a platform itself.
A great place to start with learning how to edgeguard Fox and Falco is with Kira's tutorial video, as well as with the followup video. This section is incomplete, but sometime hopefully soon I'll go into more detail about specific situations and strategies for edge guarding.
Recovering from offstage against Fox consists of mostly the same mixups used in all matchups. The largest difference is his potential to instanly kill you at any percent with a shine-spike. The most common way this happens is when Marth uses Sideb while too close to the stage. If fox jumps offstage attempting an unsafe shine-spike (possibly while predicting you to side-b) you can sometimes kill him with a Fair followed by an edgeguard. You can also hit him with a well-timed side-b itself if you cant afford to lose your height.
If you're close to the stage and slightly below or roughly at the height of the ledge you have the option to air-dodge onto the stage. This is often overlooked or forgotten completely as a recovery option, but is a great mixup (as well as a option to survive a Marth Killer).
If you're too low when offstage your only options are to either sweet-spot the ledge with Upb, or to land onto the stage with it. Landing sweet-spot Upb's is a terrific skill to have, and will save you against many edgeguard attempts (Including the Marth Killer). Getting a perfect sweet-spot is easier on stages with walls at the ledge because they allow you to "ride" the wall with Upb, avoiding the need to perfectly space yourself horizontally as you would on Battlefield for example. If you choose to land on the stage and you know the Fox will attempt a punish you should be prepared to Amsah Tech attacks like his Dsmash.
Note that stage preferance largely depends on playstyle, and much of the arguments regarding stages are either subjective or openly debated. Don't take my opinions on stages as fact. With that in mind...
The large amount of space and a lack of platforms combined with Marth's general ground dominance and powerful punish game makes Final Destination a good pick in most matchups. This is particularly true against Fox, due to his lack of options for escaping chaingrabs. Assuming that you're skilled at chaingrabbing, I consider this to be Marth's strongest stage in the matchup.
Dreamland has the highest side platforms of the legal stages, as well as the largest blast zone. Even though it has plenty of room for movement, it's for these reasons that Dreamland is often considered Marth's weakest stage in general, as well as in this matchup.
Beyond Final Destination and Dreamland the positives and negatives of the stages become even more opinion and playstyle dependent. It's my opinion that against Fox: Pokemon Stadium is the second best, Battlefield is decent overall, and Fountain of Dreams is second worst.