Crow

A Burst 3 Fire Submachine Gun and a debuff-leaning Nikke who lowers enemy ATK at the start of Full Burst and uses her last bullet for survival and bonus damage.
She is rarely a core pick in Story, bosses, Raids, or Arena.
She is almost never seen in top Solo Raid lineups.

When Full Burst Time begins, all enemies' ATK drops briefly, and landing her last bullet applies bonus damage to the target and Increased DEF to herself. Her Burst Skill deals heavy damage to the single enemy with the highest ATK.

Keep firing to the end so the last bullet lands.
Make use of the window when the Killing Time1 debuff applies at the start of Full Burst.
Keep Auto as the default; if last-bullet or close-range hits drop off, adjust range by hand.

There is little evidence of combos used together in the same squad in the recent meta.

Last-bullet chaining is key, so cover Reload with the Resilience Cube and Bastion Cube. Supplement Submachine Gun Hit Rate with the Assault Cube. If the cube level gap is large, use the higher-level Harmony Cube regardless of ranking.

Her own damage contribution is small. To make the most of last-bullet survival, prioritize DEF lines and put Elemental Advantage damage and ATK lower.

If she isn't a meta core pick, save your skill books, and only raise Killing Time1, Daredevil2, and The TerroristB to 4 when you use her. The Full Burst debuff and Burst damage are her core, so level all three skills together. Going to 10 isn't worth the investment.

She is almost never seen in top Solo Raid lineups. There are many alternatives for the Burst 3 debuff and defense slot, so she is not used as a core pick.

She can apply an ATK reduction to all enemies at the start of Full Burst.
When her last bullet hits, Increased DEF improves her survival.
Her Burst can deal heavy damage to the single enemy with the highest ATK.

Her damage isn't at main DPS level.
The last-bullet condition and Submachine Gun range interrupt her sustained-fire gains.
She is rarely a core pick in the competition for Burst 3 debuff and defense slots.