And everyone thought this guy will not have this treatment! Someone in YouTube has uploaded a low-quality shot of Diend transforming into his ultimate form, Kamen Rider Diend Complete Form. In this form, using the Gekijyoban card, he has the ability to summon all lead movie exclusive Riders minus Gaoh (Gee, I wonder why... *Points at Yu-Ki*).
This scene came from Kamen Rider x Kamen Rider x Kamen Rider the Movie: Cho Den-O Trilogy - Episode Yellow: Treasure of De End Pirates which stars Daiki Kaito/Kamen Rider Diend as he returns to AU Den-O World with him being chased by a Time Police.
All I can say is, for a Final Attack Ride, this in an overkill considering that he will only kill a single Rider!