Out of all moves present in the Super Smash Bros. series, the Down B specials are definitely the most interesting consdering they often times fall out of being pure attacks into the realm of counters, transformations and item creation.
Pro Smash player PG|ESAM has been crafting tier lists recently to rank each character based on a particular move, and his most recent for Super Smash Bros. Ultimate dives into the best and worst Down B’s around.
Meta Knight’s is one of the stronger in the game according to ESAM because it basically forces you to block it or give up the stage even if it is technically unsafe — and is still a bit from the top.
On the opposite end of the spectrum, Piranha Plant’s big munch is among the absolute worst. ESAM gives it credit for having armor, but that’s about the only nice thing to say about it.
You may not be able to guess who’s at the very bottom, however.
As for the traditional fighting game characters, Terry’s Power Dunk is actually rated the highest followed by Ryu/Ken’s Focus Attack and finally Kazuya’s
You can check out ESAM’s full Down B tier list below, and his full breakdown can be found on his Twitch archive.
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Source: Culled From Event Hubs.