All For One/Relationships

All For One's Brother
In the past, All For One cared deeply for his younger brother as he was the only family he had. However, All For One did insult him, labeling him as pathetic and fragile as he had his bodyguard go easy on him before imprisoning him. In return, All For One's brother had a strong sense of justice and did not back down from opposing his brother's evil deeds. To end his rebellion, All For One attempted to get him to submit by giving him a quirk, unaware that his brother already had one and his act only formed the creation of One For All. All For One's younger brother attempted to defeat him with his newly merged Quirk (now called One For All), but didn't have the sufficient power to do so.

It is unknown if All For One killed his brother in battle, but the latter's quirk was passed down to an unknown successor, in the hopes that someone in the future would eventually stop his evil older brother once and for all. Because of his brother passing on the Quirk, All For One sought One For All with each successor.

Tomura Shigaraki
All For One is grooming Tomura as his successor. He was the one who rescued Tomura from the streets after the incident of killing his family during his childhood. All For One is deeply invested in Tomura's growth and was pleased when Tomura finally developed a plan to achieve a goal on his own. Although well aware of his immaturity, he works to mold him into the successor he dreams of him being. When the police and Pro Heroes capture Tomura, All For One retaliates with force before teleporting Tomura and his friends to safety.

It is unknown whether Tomura is aware or cares that All For One killed his grandmother, however, it does appear that All For One truly cares for Tomura, having a similar relationship like All Might has with Izuku Midoriya. All For One even allowed Tomura to carry on his family name, Shigaraki, when renaming him. Instead of punishing Tomura like any archetypal villain would do to their apprentice, All For One instead encourages Tomura to simply start over as many times as he needed to and that he will always provide him with help. His care goes so far as to urge Tomura and his friends to leave the battlefield with All Might, keeping the Symbol of Peace distracted and entrusting Tomura to continue the fight in his stead.

Although All For One groomed Tomura with the intention to demoralize All Might and even scorn the lineage of Nana Shimura, it is evident that he grew to care for his adoptive son and is the only person to whom he has shown genuine love to, arguably besides his brother, even if greatly motivated by evil.

Kurogiri
Not much is seen between them, though Kurogiri seems to be loyal to All For One. All For One entrusts him into looking after Tomura and ensure that he is given the proper guidance.

Kyudai Garaki
All For One trusted Kyudai, making him his own personal physician, tasking him with making Nomus and overseeing Gigantomachia. Kyudai has been with All For One for at least a decade. During this time, Kyudai copied All For One's quirks by unknown means. After All For One's defeat, Kyudai continued to believe in All For One. It is said that All For One respects Kyudai's research on Quirks, being the only person to believe Kyudai's Quirk Singularity theory. It was revealed that Garaki took a part of All For One's name: Shigaraki. All for One puts deep trust in his physician, exclaiming that Kyudai's insatiable curiosity and inquisitive nature has always been the source of All for One's strength, and thanks the doctor from the bottom of his heart, going so far as to call him his friend.

Gigantomachia
Gigantomachia 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 initially refuses to accept Tomura as his 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. However, he came to accept Tomura after seeing his reawakening in action.

All Might
All For One detests All Might. He hates the One For All successor for incapacitating him, defeating his comrades, denying his ambitions and being called the symbol of peace for this.

He states to All Might that he needed a successor because of the injuries All Might inflicted on him from their first battle. Due to the crippling injuries All For One received he can never be in his prime again. It's also heavily implied that All For One is in an even worse shape than All Might is. While All Might's injuries limited his use of One For All, All For One is not capable of living without a life support apparatus keeping him going.

During their second battle at Kamino Ward All For One confesses that he still has nightmares and mental trauma from their first encounter from when he saw the look on All Might's face after ripping All Might's guts out. All Might seems to not only be the first to defeat All For One, but also the first to ever severely scar him mentally.

All For One enjoys belittling and ridiculing All Might, even relishing in breaking All Might's spirit by revealing that Tomura is Nana Shimura's grandson. He also enjoys watching All Might become riled up by belittling Nana's heroism and death. In their second battle, All For One aims to take everything from All Might, his image and pride by revealing his gaunt form and weakness to the public.

Even after being captured, All For One continues to play with and taunt All Might, using any and every opportunity to strike at his nemesis. Despite being defeated by the latter, All For One took his loss in stride and mocked All Might for not dying when he had the chance, confident that his pupil will become stronger to take over the League of Villains. All For One is also aware of the fact that Izuku Midoriya is the current bearer of One For All and criticizes All Might for being a pathetic teacher.

Nana Shimura
All For One thinks Nana was a pitiful woman. He mocks her commitment to ideals and disparages her strength and, by his admission, declared the latter died a pitiful death.

All For One tarnished her memory by knowingly taking in and grooming her grandson to be his successor.

Best Jeanist
All For One praises Best Jeanist's skills and proficiency with his quirk. However, he deems that his quirk requires too much skill and therefore it's useless to him. All For One blast a gust of air that, in the long run, costs Best Jeanist a lung. Best Jeanist is terrified of All For One's sheer power and skill.