Shaggy is no Risen CGV, still the best fight maybe now topped by Amatsu if not for Amatsu's poor stats. However, I think he's fairer than he seems.
His attacks don't let up and feel bullshit, but you gotta realize something crucial about Shaggy.
ALL of his attacks attack forwards. His backside is so vulnerable. You're almost always safe attacking his tail for instance. If you're on a mobile weapon, he's a bit of a pushover.
"Iwata was awesome" - Mr. Nintendo
https://i.imgur.com/krtFHol.jpg