Just stand there and full jump fair marths approach and remember to spam down b
What a good way to get Ken combo'ed. I don't believe Mew2King was having any of that at VLS.
Two things about Marth.
-Back air = god. It outranges almost every aerial Marth has, and is effortless to use to out-prioritize.
-Try to not stay predictably in the air a lot. Marth is looking for one tippered forward air or one neutral air in order to tap you into the spike, so don't give it to him.
Those are the two most important things. Another tip I'll give, for the sake of Linguini's, here, is to avoid over use of the forward air. It's incredibly slow compared to all Marth's attacks, and if they see you jumping back with it for the thousandth time, they have a number of options to stop you, like simply wavedashing into a forward smash. Abuse the back air and up air out of the shield when they're trying to double forward air your shield. The forward is VERY circumstantial against a skilled Marth player(and when I say skilled I'm referring to Marths like Mew2King, KDJ, Chillin, Azen, etc.).
Above all, it comes right down to being able to read your opponent. Marth normally has longer range than Ganondorf. Normally. It's all about finding that perfect timing for when it's Ganon's turn to outrange Marth.