Ok, looks like some people have misinterpreted my information. Toot-Toot is the worst kill confirm in the game, as Bookworm has said. Roy does have a pretty good disjoint, I said "even Roy beats GnW" because Roy is generally considered to be the worst/second worst sword character. (Although I don't really think that). Despite Roy's aerials being less negative on shield, they are still less ranged than Marth's. Also, Mario can kill, not sure were this belief propagated from, as Mario has very good Smash attacks, Up-Air to Up-B strings, and Back-Air. Fair can also kill at ludicrously low percents as well. I really do think that GnW is a character that thrives not off of being good, but off of matchup experience.
Marcina and Roy Dsicords both say Marth has a better combo game, because spacing actually can allow Marth to get 30% in a combo. Roy has garbage aerial mobility, so spacing with Roy is mainly ground-based, while Marth can space in the air as well. Marth also benefits much more from spacing well, so Roy's spacing game is actually pretty meh, as he actually is harmed slightly by spacing. Roy relies mostly off of low percent combos to rack up damage and then get a kill.
Also, to be completely honest, my answer before was mostly out of annoyance due to FeelMeUp's comment. While I respect his knowledge, that comment was just insulting.
Edit: In response to RK, yes, I know that Daigo is much more than I said he was. I just compared him to ZeRo because that was the only Smash player who comes even close to having the star-power of Daigo. Daigo himself is a FGC legend, and he truly is the Beast.