Cinderella

In Mirror Container and long single-boss fights she is considered a top-tier main DPS candidate.
Her max-HP-scaling buff and the buffs that stack during combat greatly widen her single-target damage, even within the limits of a random Burst.

On entering Burst stage 3, she briefly gains Increased ATK based on final max HP, and when she fires a Full Charge shot, Increased Charge Speed lasts until her reload ends. When a Full Charge attack hits, bonus damage based on final ATK is dealt.

Her Burst Skill deals damage based on final ATK to random enemies 10 times in sequence. If she has Beauty, the same target also takes additional damage based on final ATK, which scales with Beauty stacks.

The longer the fight, the more Beauty stacks up while her Decoy holds, and the max HP support she provides grows thicker as well. The Burst bonus damage is only large while Beauty is active, so it ties directly to fight length.

Land Full Charge shots to keep Increased Charge Speed and Full Charge hit bonus damage rolling.
Glass Slippers. Full Contact.1 is 10 random hits and can't be locked by aiming, so on single bosses use the Burst Skill while the core is exposed.
Auto is fine by default. On multi-target stages many shots tend to stray toward mobs, so pick priority targets by hand.

For Rocket Launcher reloading, prioritize the Bastion Cube; if you want both Charge and Reload, treat the Resilience Cube as the second option. If the cube level gap is large, use the higher-level Harmony Cube first regardless of ranking.

For Max Ammo and crit, fill the remaining slots with ammo, crit-rate, and crit-dmg options based on weapon, range, and whether Hit Rate is lacking.

Flawless Glass2 and Glass Slippers. Full Contact.1 determine her damage, so raise Burst and Skill 1 first. For passive growth, also develop the part that sets up Decoy and Beauty stacks from the start of battle.

Put her in the main DPS slot for stretches where you pound on one enemy for a long time, such as single bosses, Tower, and Mirror Container. On mob-heavy stages, her random Burst and Rocket Launcher traits lower her priority. In Arena she also goes into lineups aiming for single-target damage and durability.

On entering Burst 3 she gains Increased ATK based on final max HP and bonus damage on Full Charge, making her basic-attack windows solid.
Glass Slippers. Full Contact.1 hits random targets in sequence, so you can't lock targets by aiming, but once Beauty has stacked, large bonus damage plus a Mirrors the stack count effect apply to the same enemy.
With Decoy and Beauty, the longer the fight, the thicker her HP-side support becomes.

Her Burst hits random targets, so against multiple enemies her damage tends to spread out.
Beauty and her Burst's bonus damage only kick in properly once stacks build while her Decoy holds, so in short fights the impact is weak.
She carries the usual Rocket Launcher burdens of reloading, Full Charge handling, and landing shots.

In long single-boss fights like Mirror Container, you end up choosing between Cinderella and Ein for the same Burst 3 slot; if mobs or multiple parts show up often, Cinderella is less demanding to run.