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.

Tomura Shigaraki
All For One is grooming Tomura as his successor. He was the one who rescued Tomura from an incident during his childhood. All For One is deeply invested in Tomura's growth and was satisfied when Tomura finally developed a plan to achieve a goal on his own. When the police and Pro Heroes targeted Tomura, All For One retaliated 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, as before he teleported Tomura away for the last time he told his pupil to continue the fight without him.

All Might
All For One detests All Might, as he is the One For All successor who incapacitated him and defeated his comrades. All For One hates All Might for being the symbol of peace and for denying his ambitions. He claimed to All Might that he needed a successor because of the injuries All Might inflicted on him. Due to the crippling injuries All For One received, he was limited, and could never be in his prime again. It's also heavily implied that All For One is in an even worse shape than All Might as, while All Might's injuries limited his use of One For All, All For One didn't even seem capable of living without life support apparatus keeping him going. Another reason, All For One hates All Might is also due to trauma and fear. Even after their fateful confrontation which lead to All For One's first defeat, All For One claimed he still had nightmares and mental trauma from the event. All Might seemed to not only be the first to defeat All For One, but also the first to ever severely scar him mentally.

All For One seems to enjoy belittling and ridiculing All Might during their confrontation, even relishing in breaking All Might's spirit by revealing that Tomura is Nana's grandson. 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 Tomura Shigaraki to be his successor.