Kamen Rider 4

Kamen Rider 4 is the fourth Kamen Rider created by Shocker, succeeding Kamen Rider 3 and the Shocker Riders, and the secondary antagonist of the Kamen Rider web miniseries D-Video Special: Kamen Rider 4, though he first appeared in a post-credits scene in Super Hero Taisen GP: Kamen Rider 3.

Super Hero Taisen GP: Kamen Rider 3
Kamen Rider 4 appears in a post-credits scene, where the Great Leader of Shocker overlooks him being operated on.

D-Video Special: Kamen Rider 4
It is revealed that Kamen Rider 4 was created by Shocker using parts from the recovered History Modifying Machine, resulting in Drive and the other Riders being caught in a series of time loops.

By the fifth loop, Kamen Rider 4 was completed and sent out to confront the Riders. He attacked Shinnosuke in the Tridoron using the Sky Cyclone. Drive confronts 4 alongside Faiz and Zeronos, but 4 overpowers the three Riders and kills Shinnosuke as he is defending Faiz.

After the timeline resets once more and a sixth loop begins, Kamen Rider 4 confronts the three Riders once more when they arrive at a factory owned by Shocker. While Faiz and Zeronos fight the other Shocker forces, 4 battles Drive and has a more even fight with him than the last time, but Drive is still unable to overpower him. The loop then ends after Kiriko is killed.

In the final loop, Kamen Rider 4 faces off against Drive once more in the final battle. After a brutal fight, Kamen Rider 4 has his Sky Cyclones destroyed and his leg broken before Drive attempts to finish him off with a Formula Drop Kick. 4 attempts to deflect it with a Rider Punch but Drive manages to overpower him by increasing the output of the Shift Brace, overwhelming and destroying the Shocker Rider.