episodes 1-10 as leader of the Hakaida Squad,
episodes 11-46 as an agent of the Shadow
At the end of episode 10 after Silver Hakaida has been destroyed by Blast End, Kikaida 01 tries it on Gill Hakaida. Instead of the normal explosion there is a bright white glow and the laughter of Big Shadow is heard. Gill Hakaida appears to have been destroyed, but in fact he was taken to the Shadow's headquarters, where he is kept in chains until he agrees to cooperate. He ends up in chains again in episode 20, after attempting to kill the Big Shadow.
Gill Hakaida pretends to serve Big Shadow but in reality he schemes is to revenge his 3 "brothers" by destroying 01, no matter what Big Shadow says.
In episode 19 Professor Gill's ghost appears to make Gill Hakaida stronger. It doesn't help. In episode 20 Kikaida 01 uses Blast End on Gill Hakaida. The Big Shadow is able to save his head, and restores his body. The restored Hakaida pledges allegance to Big Shadow. In episode 37 Gill Hakaida appears to be afraid of Bijinda and is clearly jealouse of Waruda.
Note: In the show Gill Hakaida is refered to simply as "Hakaida". I use Gill Hakaida so as not to confuse this character with the original, Dr Komoyoji, Hakaida from Jinzo Ningen Kikaida. The two characters had very different personalites. For example, the original Hakaida would not take hostages or attack a helpless enemy, this Hakaida has done both. The original Hakaida was a more complex character, I think that made him more interesting. Saburo, the human form of the original Hakaida, does not appear in Kikaida 01.
Gill Hakaida's special combat techniques are "Outlaw Kick", "Guillotine Drop","Magma Upper" & "Hakaida Throw". He could also use "Satatnic Darkness" to plot out the sun to keep the solar powered Ichiro from transforming into Kikaida 01 (episodes 4, 7, 10).
Gill Hakaida fell in love with Mermaid Princess, to him the most beautiful robot. She was actually one of the ugliest.