User blog comment:OneOfThoseCrazyGirls/5 Villains Who Must Appear in the Arrowverse/@comment-31125534-20180422122919

Did they seriously mention Lesla-Lar? Supergirl's first proper villain? I'm impressed.

Anyway, no, Nekron wouldn't work. You'd have to introduce too many storylines and characters: the Green Lantern Corps, the emotional spectrum, GL's villains, the remainder Corps... Geoff Johns spent five years setting up Blackest Night. You'd easily spend one year worth of plotlines setting it up, and fans would wonder when and why their favorite show got changed into a Green Lantern series.