Yaiba of the Darkness

I think another Boukenger villain that is worth mentioning would be Yaiba of the Darkness. At first glance he may seem stereotypical but some things in him made him quite unique. For instance, no other villain yet in Super Sentai history ever tried to unlock the darkness in a ranger or something. Not even Five Red's confrontation with Garoa had that kind of rivalry.

How he existed is not clear but presumably, he is an android judging by the metallic-like face he shows created for modern day purposes by Shizuka. But for one thing, he and Inou Masumi (as a child) had a history. He killed a group of adventurers and took advantage of the fact Inou Masumi used them as a shield for his own purposes.

Inevitably, this sparked a rivalry between them. He was also the type to take advantage of the situation for his own profit and he attempted to overthrow Gekkou while in secret. As the series went on, he finally launched his plan to turn Gekkou into the devil bird as so he could destroy both the Boukengers and Gekkou. When Shizuka tried to assassinate him, he had the upper edge but strangely wasn't able to kill her.

Not soon enough did he decide to intervene with Ryuon's plan of the Three Headed Dragon of Darkness candlestick and used it on his rival Bouken Black hoping to achieve his true purposes of ruling the world for himself. However Bouken Black who always had the light within him countered that power and inevitably defeated him probably out of vengeance. But again, he deserved to be put to death for his mass murders. But before death, he swore that the darkness will never disappear in Bouken Black before descending into Hell.