Rapi

She is not a meta core Burst 3 DPS. She's an SR for early Story and new lineups, competing on single-target damage and taunt with Missile1 and Warhead Volley2.
FF FormationB raises her own ATK when she is hit frequently. Her investment and Overload priority are low.

Her structure: Assault Rifle sustained fire builds FF FormationB, and Missile1 and Warhead Volley2 deliver damage, taunt, and a self ATK buff to the 1 enemy with the highest final ATK.

FF FormationB raises her ATK every 20 hits taken, and Missile1 deals damage and taunt every 20 sec. Warhead Volley2 is her Burst Skill, with a cooldown of 40 sec.

Sustained fire can be left on Auto.
Manually aim so Missile1 and Warhead Volley2 land on bosses or elites with high final ATK.

She's sometimes used to fill an empty Burst 3 slot in new Story content. She's almost never in core Solo Raid, meta boss, or Arena squads.

Go with the Resilience Cube for sustained fire and reloading, the Adjutant Cube for charge and firing tempo, then the Assault Cube for Hit Rate and Elemental Advantage hits. If you have a high-level Bastion Cube, use it as the second option.

As a low-usage SR, her Overload priority is low. Only if you raise her, set Elemental Advantage damage and ATK lines, and fill the rest with Hit Rate and Max Ammo.

If she isn't a meta core pick, leave her at 1/1/1. When raising her, leveling Missile1, Warhead Volley2, and FF FormationB evenly to 4 is enough.

She's for early Story and filling an empty Burst 3 slot for newcomers. She rarely goes into core Solo Raid, boss, Tower, or Arena lineups.

Missile1 deals damage and taunt to the enemy with the highest final ATK.
Warhead Volley2 provides Burst damage and an ATK buff for herself.
FF FormationB raises her ATK as she keeps getting hit.

Her skills target the 1 enemy with the highest final ATK, so they're easily wasted on cover or mobs.
As an SR from the old meta, her damage is low for the investment.
She's rarely a core pick for Raids or Arena.

Her skills and role differ from Rapi: Red Hood. See the separate guide for Red Hood.