Onion Knight Refia is a decent but largely unremarkable chainer with some major flaws regarding her chain skills. First of all, to define Onion Slice itself:

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This is the main variant, shared by the likes of Onion Knight, Sephiroth, Loren, Hyoh and several others. However, there are couple of other forms. First off, Onion Knight Refia's Onion Shredder:

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Addtionally, there is Onion Knight's Onion Slice 2 when used after an enhanced Splendor skill:

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From what I've tested, none of these Onion Slice sub-families can chain across each other completely, and they definitely can't spark chain in that configuration. This problem was attempted to be remedied for Onion Knight Refia in global by changing Hacked to Pieces to be the original Onion Slice frames instead of Onion Shredder frames; in reality, this doesn't actually solve anything since Hacked to Pieces can only be used the turn immediately after a self imbue or Onion Shredder chain. Ergo, if you want to chain with someone like Loren with Onion Knight Refia, you're limited to doing it immediately after setup or resorting to a very weak Full Speed Bladeblitz chain on demand.

To add insult to injury, Onion Knight Refia's most powerful skill is an otherwise dupe only cooldown chain, Onion Meteor; extremely close in frame data to Onion Knight's similarly themed Onion Chop cooldown, but not enough to chain properly. Overall, Onion Knight Refia isn't particularly powerful, but her easy access to multiple elements and imperils along with high burst damage via cooldown does somewhat compensate for her poor partner access and middling average damage.

What I would have liked to have seen for her is a reversal of what Gumi attempted in order to fix her: keep Hacked to Pieces with its own frames if they like, but make Onion Shredder match the original Onion Slice frames; this would allow her to chain with the original family perfectly, while dealing slightly more damage with a dupe (9x mod vs. 10x mod after setup). Additionally, matching Onion Meteor's frames to Onion Chop would hardly be game-breaking, and give her a little more non-dupe flexibility.

P.S. Cysidus is making me mention the fact that Hyoh's Ruthless Blade skill is technically two chain families in one: the combined ST portion is Onion Slice, but the 6 AoE-only hits will also form a complete chain with W skill due to how much Onion Slice frames overlaps with itself (which is why it is difficult to manually chain).

What would you have liked to have seen from Onion Knight Refia?