Delta has to be the least memorable non-movie Rider in the entire franchise's history. Scissors and Gai made more lasting impacts than Mihara.

I think you're forgetting Dark Necrom P from Ghost. She only existed for like 20 seconds, but still, pretty bad.

That and it's whole "Delta is so crazy powerful, you get powers even outside the System" was forgotten almost immediately.

Wait what? I don't remember that. All I remember was that scene where he choked Faiz and Kaixa and he seemed really tall, and the gun he spoke into.

I'd say Delta was memorable up until the point where Mihara got the suit. By that point it was clear they had no idea on what to do with Delta.

Yeah, when first introduced the Ryuusei School kids were passing it around / fighting over it / losing their minds - a bit Lord of the Rings-ish, really, with Delta being the desirous ring. They kinda go evil over it and get friggin' electricity blast powers when not in the suit. This is never touched upon again after this episode! Delta is the one main plot device they fumbled.

I think they tried to bring that plot point back when Mihara got the suit but like Mihara himself it was something that was fairly quickly forgotten.

Totally don't remember that. Mihara sucked, though; I kept waiting for Rina to rip the belt off him and finally become Delta fully realized and - for about five seconds - she did but, that was the only time because Kamen Rider is for BOOOYSSS.

The only things I really remember about Delta is that one of the stronger Orphenochs was the first user (I think Dragon?) and that it was the only Kamen Rider design in all of Faiz I actually liked.

I'd find it really funny if for the next Taisen movie, they got the guy who played Mihara back as Delta, and actually developed him as a character and resolved the last hanging plot thread of Faiz in a semi-satisfying way. Killing the King, of course.