I've been playing a lot more Agitha lately and she's really starting to click with me :3
As someone mentioned before, against a boss spamming XXY-B repeatedly when the weakpoint comes up will shred it down pretty darn quick so I've been destroying a lot of monsters with it.
Against humanoids I was starting to get annoyed at how easy it is to drop the butterfly combo (XXXY-YXXXY) so I've been playing about with other ideas.
I initially tried the XXY-B spam but due to the summon itself not hitting your target they'd often shake out of hitstun and slap me.
So far the most effective is to start with XY to launch and if they go up in the air you immediately follow with XXY-B: you'll almost always air-juggle them with the second X hit putting them back up long enough to be hit by the beetle without being able to recover. Repeat this sequence ad-nauseam :3
The only person this doesn't quite work with is Volga, because he often somehow air-recovers away from the second hit of the beetle (something nobody else seems to be able to do
)
You can actually infinitely juggle all humanoids very easily just by doing XY over and over again against a wall but the damage doesn't seem all that great and though I've not tried it yet, you could likely follow the XY launch with a butterfly combo (YXXXY) which would be a much safer way to lead into it than the whirlwind combo I mentioned earlier (XXXY)
Her best crowd clearance, if you can find space to pull it off without getting interrupted, seems to be her XXXXY which makes her jump and then sends a huge beetle along in a line infront of you hitting everything in it's path, then auto-launches you to butterfly which you can then crash somewhere (Y button) for even more AoE. Generally though you don't want to be doing the third X attack (whirlwind) anywhere near enemies as not only does it lock you into the non-cancellable animation but you can be hit from the ground while doing it (even though you're up in the air :/ )