User blog comment:OneOfThoseCrazyGirls/5 Villains Who Must Appear in the Arrowverse/@comment-24152851-20180424034530

Onomatopeia was originally going be on Arrow, but he got replaced with Mr. Blank. Kevin Smith said he'd be up for having him on the Flash. But tbh, he'd still be a better for Arrow. Would have been much better than Cayden James or Dragon

Absolute yes to Nekron. Arrowverse crossovers keep getting bigger and bigger, so aside from a Crisis on Infinite Earths adaptation, the one to really top it would be a Blackest Night adaptation. It's perfect given how many dead characters Arrowverse has. Although they might have to introduce one Green Lantern first, doesn't have to be Hal Jordan and maybe as an animated series or something.