League of Villains
Gigantomachia is fiercely loyal to All For One. He was his bodyguard when All For One controlled the world from the shadows, and said loyalty has not waned despite All For One's downfall. For his part, All For One considers Gigantomachia an essential piece for Tomura Shigaraki and the resurgence of the League of Villains. Because of this, All for One hid Gigantomachia in the mountains as a means to help preserve his dreams.
However, the same loyalty to All for One that makes Gigantomachia useful also makes him difficult to control for others. He refuses to accept Tomura as successor because he believes that Tomura is not All For One's equal. It is noted that a recording of his master’s voice can quickly soothe him to the point that he will purr. 
Daruma is in charge of controlling and monitoring Gigantomachia after All For One decided to hide him after foreseeing his inevitable downfall. Daruma knows that Gigantomachia is extremely loyal to All For One, and therefore controls him with recordings of his master's voice on the radio that Gigantomachia carries on his neck. Daruma at times refers to Gigantomachia as "Machia". Daruma believes Gigantomachia is useful to Tomura's goals and refuses to lend his full support until Tomura gets Gigantomachia to submit.
Knowing that All For One chose Tomura as his successor, Gigantomachia wants to serve him, but cannot accept Tomura's comparative weakness. Gigantomachia is driven to tears by the disparity. Finding him uncontrollable, Tomura states that he doesn't want Gigantomachia.
However, after Tomura's conversation with Daruma, he learns that Gigantomachia is a necessity for his plans and he must get Gigantomachia to submit to him. Upon being warped back, to Gigantomachia's location, Tomura tells him that the “future king” is here. Amused, Gigantomachia replies that a king should inspire dread, be admired and be strong.
They resume fighting for a month and a half. Gigantomachia continues to call Tomura's attacks weak while Tomura becomes more steadfast in getting Gigantomachia to submit.
Gigantomachia later pursues Tomura to Deika City to finish their battle. However, he instead witnesses the conflict with the Meta Liberation Army and Tomura’s fight with Re-Destro. He is left in awe at Tomura's embrace of villainy and his great power. He finally acknowledges Tomura after the latter not only defeats Re-Destro but destroys half of Deika City. Gigantomachia then shed a tear, as he finally saw what All For One did in Tomura.
- ↑ 1.0 1.1 1.2 My Hero Academia Manga: Chapter 221.
- ↑ 2.0 2.1 My Hero Academia Manga: Chapter 222.
- ↑ My Hero Academia Manga: Chapter 223.
- ↑ My Hero Academia Manga: Chapter 238.
- ↑ My Hero Academia Manga: Chapter 239.