Uh, well, for one, you should play on neutrals because Marth generally does better there. There's no huge advantage to playing even on Mute City against someone like Ganondorf.
Your wavedashes are really short. Like... REALLY short. Work on airdodging closer to the horizontal. Marth's perfect wavedash is like... ten times longer than that. No joke.
Also, don't roll so much. Rolling completely removes any pressure you may have had on your opponent.
Your Marth is very... I dunno, passive. I feel like you're charging up too many things that will not realistically hit, like at 0:37. Be more proactive in your combo'ing and whatever else.
Against non-fast fallers and people at high damage (or both) I would seriously suggest not using the Dancing Blade. It's fairly easy to DI out of and not as safe as you might think.
Fun trick, if you grab them at extremely low damage, you can fthrow to regrab. Eventually they can learn to break out of it through DI and/or buffered dodges, but they can't really punish you for trying and it's free damage.
Use the dthrow, not the bthrow. Except in super special circumstances. Trying to spike Ganon into the road is not a special circumstance.
You're getting hit by the Wizard's Foot a lot. Yeah, it's fast, but if you watch your opponent's movement and spacing, it's pretty easy to tell when he's about to use it. Which brings me to another point.
Your approaches are way too readable. Dash dance or something, mix it up.
Also for free damage, smack people after you grab them. Generally, I go with once per fifty damage, but it's up to you. Listen and see if they're trying to wiggle out, too.
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