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 label 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 but this 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 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 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. According to All For One, All Might had took something from him long ago resulting in his hatred of him but its unknown what it was.

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.