I have to agree, Marth spike is really hard to land. But still, 2 spike are 2 spike.
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Also the stragegy you use depend of your character:
Marth: You keep using U-Thow even tough it's combo into nothing.
Roy: You keep spamming Smash, which after some second become to be predictable.
Sheik: You try alot to Up-Throw-> U-air or go and then try to regrab me. Which can be predictable. Also, you seem to not correctly use Bouncy Fish.
For all: You try always to go YOLO on me in the air and try to stop my attack with a F-air. Which end get you hit.
There is maybe others but that's the one that i see the most.