Doktor G

Doktor G / Kani Laser is Destron's first general in a knight armor who originated from Germany and was given charge to oversee their operations in Japan. He is the leader of the Mechanical Army. He wields a battle axe, a short sword, and a knife. In the comics, his scorpion-shaped helmet could transform into a deadly scorpion, but this didn't happen on TV. Most of his monsters are cyborgs that are the same type as Destron Leader's cyborgs. Pronounced his enemy's name "Kamen Raaaaida V3!". After numerous failures, Doktor G summoned the spirits of his dead, evil warriors to transform him into Crab Laser for his final battle with Kamen Rider V3. Despite putting up a heroic battle, he was destroyed by V3's V3 Tailspin Return Kick.

V3
Doktor G arrived in Japan after he was contacted by Great Leader of Destron who gave him orders to oversee their operations and to defeat Kamen Rider V3, Shiro Kazami.

Doktor G was responsible for the resurrection of Shocker's key figures (Colonel Zol, Doctor Shinigami, Ambassador Hell, and General Black).

Endgame
After so many of his plans were thwarted by V3 and his laboratory was destroyed by a special Interpol group known as the "Destron hunters." He personally confronted the hunters and killed them all (except for Ken Sakuma who was saved by V3).

Doktor G set a trap for V3 as an act of redemption for his failure as a Destron Commander, he kidnapped Tōbei Tachibana and the members of the Kamen Rider Scouts to lure V3. Doktor G summoned the spirits of his dead, evil warriors to transform him into Crab Laser for his final battle with Kamen Rider V3. Despite putting up a heroic battle, he was destroyed by V3's V3 Tailspin Return Kick.

Decade (Super Hero Taisen)
This version of Doktor G is a knight armored general of the revived Dai-Shocker in Super Hero Taisen. He's the second in command of the organization, bellow only its Great Leader, and standing above the other Great Commanders recruited by it. He wields an axe in battle and is able to assume the form of the Inhumanoid Kani Laser, the modernized/Narutaki version of Kani Laser.

He is the driving force behind recreating Dai-Shocker, reviving and recruiting past villains and placing Tsukasa Kadoya, Kamen Rider Decade, as leader for the express purpose of defeating Dai-Zangyack and its leader, Captain Marvelous, Gokai Red and also the leader of the Super Sentai team Kaizoku Sentai Gokaiger. His Kani Laser form was much stronger than the original, resisting against the combined forces of various Sentai members and Riders, including Kamen Rider V3 himself, who defeated his previous incarnation. In the end, he was defeated by the combined efforts of Kamen Rider Decade, Ryuki, Blade, and the Goseigers, who gave the three riders new Gosei Cards. However, after being defeated, his appearance changes to Narutaki, who tells Decade that his journey will continue and vanishes behind a dimensional wall.

In fact, this version of Doktor G is just another one of Narutaki's disguises, similar to the Colonel Zol guise that Narutaki used when he joined Super Shocker. Unlike that time though, here Narutaki showed abilities and powers not only similar, but significantly stronger than the original's.