I don't care for DFO, since I dislike when stories tie every important character to the plot together like that. "Oh I'm really So and So's secret brother, well I'm his daughter from the future, I'm the alternate timeline version of him where he lost." Then you just got the other guy whose like, "Hi, I worked down the corner from you and got dragged into this. Guess I'll just go be unimportant over here." Because unless there's some magical fate/destiny shit going on, then there should be a bit of randomness to life. But because I won't turn away from a good story.

Dad for One: Izuku was born with a powerful pyrokinesis quirk and while DFO did love his child, his plan to take over the world was more important. As such he took his son's quirk from him, which coincidentally was the extra power he needed to kill All Might in their confrontation, not that he saved himself from any pain as it left him severely burned and crippled in the fight. But he was that much closer to succeeding.

Izuku after the news that All Might died fighting a really powerful villain, fell deeper into a depression, the strongest of the strong lost. Bad guys were running rampant, people lost faith in heroes. Then it happened one day when some bad guys broke into his apartment, they did horrible things to his mother and made him watch, they hurt them both before one of them suggested they kill her in front of him just for laughs.

Izuku stopped being sad, he couldn't there was no one there to comfort him anymore, no one left to care if he was happy or sad.

So he got angry and he pulled out the books he had written on quirks. He took a different approach, instead of analyzing them to find out ways to improve, he found weaknesses.

With lawlessness on the rise, Izuku was able to acquire a pistol relatively easily. Then one night after careful planning he struck. 3 shots to the neck of the Diamond Head Gang, notorious for having think gemstones on their heads that allowed them various powers and they were dead as his mother.

For his first kill he didn't feel too terrible about it, he thought he would feel awful but in retrospect the first death he saw was his own mothers, and she was a good, innocent woman. These were horrible villains, so why should he feel anything but contempt for them

All For One, was prepping his plan to take out the last Bastion of Heroism, U.A. who was constantly spitting out new heroes in the hopes that they could stem the tide until a new symbol of peace could arise.

He had sent Kurogiri out to collect people for his disciple Tomura Shigaraki to command, when the portal user appeared.

"Sir, I checked on all the locations, they're, dead," Kurogiri reported. "All of them, Toga, Twice, Muscular. Everyone executed."

"Who could be doing that, maybe that blasted Eraserhead and some of the other underground heroes?"

"No, a camera caught a glimps of the person in a reflection," Kurogiri said producing a photo. "He's not in any hero database."

All for One gasped as he look on the face of his own son. His progeny was systematically dismantling his empire, by murder. For a moment the room was silent, before loud laughter filled the air as All for One found the true irony in the situation.