Guilty: Mighty Bunny

A Water Burst 3 DPS who serves as the main DPS of DEF-ignore squads in Solo Raid against Fire enemies (Water has the advantage).
With DEF-ignore buffers like Flora (Favorite Item) and Takina, she deals damage just below the top Water tier, and in Water-weak Solo Raid she appeared in most top records as the 4th and 5th squad DPS together with Sin: Swift Bunny.
She has no AoE damage and requires manual mode switching, so she is hard to use in story and Arena.

Battle starts in Bunny Mode: Stance, and each time Full Charge is held for 1 second or more, she alternates between Bunny Mode: Engage and Stance. In Engage, Chain Release makes normal attacks and Mighty Stomp deal DEF-ignoring damage, and each Full Charge hit adds DEF-ignoring extra damage. In Stance, Chain Enhance raises attack damage and Charge Damage, and each Full Charge hit adds extra damage. In either mode most of her damage comes from extra damage on each Full Charge, so Charge Speed is her damage.

Her Burst Skill changes her weapon to Mighty Stomp, a 1-shot enhanced round, grants that 1 shot a big Increased Charge Damage, then grants increased attack damage for 10 seconds. When Guilty switches modes, Bunny Mode allies in the opposite mode switch to the same mode, so Sin: Swift Bunny in the same squad matches modes without separate control.

Right after battle starts, hold Full Charge for 1 second or more to switch to Engage, then leave her on auto.
When controlling manually, holding Full Charge more than 1 second switches back to Stance, so fire as soon as Charge fills.
In fully automatic Arena, she cannot switch to Engage.

Fill the Burst 1 slot with Moran (Favorite Item) or Liter.

Use Resilience Cube to chain Full Charges without interruption.

Full Charge count equals extra damage count, so prioritize Charge Speed; 1 Max Ammo line is enough.

Her mode-specific extra damage is on S2, so raise it to 10 first, then Burst with Mighty Stomp damage and increased attack damage. Raising S1 only grows Increased ATK while mode switching stays the same, so it is low priority.

Used in DEF-ignore squads in Solo Raid and Union Raid boss fights against Fire enemies (Water has the advantage). As a single-target DPS, she does not fit story progression.

In Engage, her normal attacks, Full Charge extra damage, and Burst all deal DEF-ignoring damage, so she gets the full effect of DEF-ignore buffers.
Sin: Swift Bunny is the only Water DPS sharing DEF-ignore buffers with her.
The higher her Charge Speed, the more extra damage hits she gets.

She has no AoE damage, so she is weak in stages with many mobs.
You must switch modes manually, and holding Charge too long changes mode unintentionally.
She is not a DPS who dumps damage into Burst, so crit buffers do little for her.