From SmashWiki, the Super Smash Bros. wiki
Overview
Hitbox duration of Marth's forward smash.
All 4 hitbox frames together
Marth does a overhead slash, doing 14% at the base, and a high 20% at the tip with very high base knockback (the 2nd highest among forward smashes, only after Pichu's), but with lower knockback scaling. This attack is fast with great vertical and horizontal reach, and high power when tipped, with a tipped forward smash being capable of reliably KOing under 100%, and can even KO under 75%. Additionally, the tipper is not that difficult to land when spaced properly, with its rather large hitbox size. All of this combined with its ability to edge-guard opponents rather easily makes this one of best forward smashes in Melee. However, if the move is not sweet spotted, it deals much lower damage with moderate knockback, and can have difficulty KOing under 150%. Also, since this move has a large amount of ending lag, the move is very punishable if whiffed and/or not spaced properly. Nonetheless, it remains as Marth`s main KO move (other than his down aerial), being Marth's strongest attack outside a charged Shield Breaker, while having the start-up and reach to be easily landable.
Hitboxes
Timing
Charges between
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3-4
|
Hitbox
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10-13
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Interruptible
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48
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Animation length
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49
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