Was Grand Lord Crisis Really The Great Leader?
In the Showa era, there was the mysterious villain known as the Great Leader. Either this guy frequently changed forms, used extensions of himself or just used decoys at the end of most Kamen Rider series. As I'm trying to watch more of the Showa era (and I prefer the Heisei era) there's always this "Great Leader" guy I keep hearing about. Just remember, this is a fan theory and nothing more. Toei hasn't released any official word about this one. Also note that just because the late Naya Goro voiced him doesn't automatically make him the Great Leader.
With my rather limited knowledge of Kamen Rider's Showa era from Kamen Rider Black RX, there's some hints that Grand Lord Crisis is the Great Leader. Maybe, he's not Gorgom's founder since Kamen Rider Black was supposedly separate from the rest of Showa but Black RX created a retroactive continuity for that. The 10 other Kamen Riders of the Showa era were seen training for the final battle with Crisis, that they were fighting Crisis worldwide which may hint that Grand Lord Crisis is indeed the Great Leader.
Does anyone remember the existence of Colonel Tasmader? While Tasmader felt like he was an inspector of the Crisis Empire but he was in reality a secondary body for Grand Lord Crisis. The show doesn't make it too clear whether or not he's got his own free will (but he seems to have it) or he's just a puppet of Grand Lord Crisis. But the final episode hinted that Tasmader is nothing more than an empty shell. It's similar to how Demon King Psycho in Sharivan used Umibozu/Demon King Psycho as a second body. Based on Tasmader's existence as a secondary body, I have my wild theory that the Great Leader has used every other incarnation he has merely as an extension of himself and Tasmader is just one of these many bodies he's used in the past.
So I guess Grand Lord Crisis is an insane, double-crossing creature who manipulated every organization he could. It's possible that he simply manipulated some humans to do his bidding while tricking them into creating Crisis Empire's ideal world. So it's highly possible that back in the first Kamen Rider he was simply giving orders from Crisis World but his subordinates are unaware of who he is or what he is. Then he started double crossing anyone he could until he could create the ideal world. When all else failed, he decided to send his bumbling subordinates to directly attack Earth. When they kept failing, he used Tasmader as a secondary body to make sure things go according to plan but he's still a major moron of a leader.
During the events of Black RX, he mentioned that as long as evil exists he may return someday and a new Crisis Empire may be formed. But after the return of Kamen Rider after an 11 year hiatus with a new writing format, one can see that the Great Leader only returned in non-canon crossover films. In the main continuity, the Great Leader hasn't made a single reappearance. No, he's not Daguva in Kamen Rider Kuuga. He hasn't made a single reappearance in the Heisei era series but only in the crossover movies. I guess Toei just got tired of him and decided to make him a punching bad in crossover movies. So I guess with Grand Lord Crisis destroyed that was the last of the Great Leader himself.