Being a marth main in melee I think the ditto defines whether or not your actually a good marth. Not that it does, but its my personal opinion. Therefore I grind with all my local marth players alot since its also my fave MU being 80-80 and amazing.
Anyways technically the main problems in a marth matchup are the approach.
1.Approaches can be started with any of the following
a. Movement with wavedashes and dash dances to a GRAB
b. Down tilt
c. Bait and punish, (generally off of movement)
Down tilt is the best lagless move to start an approach off of. It can be done fastest out of a wavedash
or you can dash dance and simply hold down on control stick to crouch cancel the dash and then
hit a slower down tilt.
This is my favorite option because it leads to so many options.
If opponent shields, go for a wavedash grab. If he doesnt, you can combo into a forward tilt into fair... so on death
if he wavedashes back you get stage control and win anyways.
The main problem with marth IMO is that he doesnt have a good approach because if he misses his first hit
his moves come out so slow that your dead in an experienced set if your opponent gets in.
Therefore most of marths game is really about letting the opponent make a move or forcing him to.
Thus the need for CRISPY movement to make them bring out an attack and then rush a JC grab or punish depending on what they do.
JC Grabs with marth having the most effective grab in the game means in a ditto you really just playing out who has the better grab. (btw JC grabs are a must!!!!)
This means that to win an approach and ultimate lead into a combo off grab you need to play PATIENT wait for your opponent to swing then...
grab uptilt, aerial, aerial, aerial, Dair or edgeguard. PUNISHment
P
hope that helps!!
you can practice alot of this on CPU marth too since his grab as a CPU is better in reaction than standard players.
After you have approach options down, simply learn the combo weight and what moves you can do, then
focus all out on punishment (combo leading to death) which is the most important thing as Armada says
-Million <3