Callousnymph - Larxene, one variation of her sobriquet.

daddyslittleheadache - Refia, uh... self explanatory XD

Declaregamuza and Destroytiburon, Nel and Halibel respectively, it's their activation commands, in English.

Doesthissmellofchloroform - Hojo. The joke is that it's the only chat up line he knows.

GracefulDahlia - Marluxia, it's his weapon.

Hearstheplanet - Aerith, because she uh.. does.

Innatelunacy - Saix. He's a moon powered berserker, in his canon. He doesn't need moonlight to do it in Spira, fortunately, but the name stays.

Joinmyreunion - Kadaj. It's his shikai activation command, and a nod to his obsession with Jenova's reunion in canon.

LawlietSchiffer - L. This would be his real name XD

Lilinette - ... Yeah.

NotJustAnyOldDude - Xigbar, a quote of his from KH2.

Palehornedprince - Yylfordt, activation command.

Sipthehoneylikeabutterfly - Szayel, iirc it's a translation of a line from one of his songs.

Soundfivebitch - Tayuya. You may stress either five or bitch for accuracy.

TaciturnStalwart - One of the newer translations for Lexaeus, formerly known as the Silent Hero.

Thatsit - Ignis. Ten minutes playing FFXV will explain that one.

Theprinceofpain - Noctis. Gladio calls him this when he kills a thing in a fight.

Tozasemurcielago - Ulquiorra. Activation command, original language(s).

There's also Averagepinkhairedcatgirl for Bonita, a childhood friend of Ulquiorra's, who is a uh... pink haired catgirl.

And NoirDiem for the OC, Noir, which finds the name amusing, and kept it.

pffffffffft Refia

and omg the Ignis one, nice.

Jim clocked its availability XD

Nice job. 8D