Having become a villain, and wanting to get a quirk or two, his body had to be prepared. His small, frail body couldn't handle a new quirk, nevermind multiple. This new workout had to include a healthy diet too, because he hadn't been eating at all. He hadn't been taking care of himself. He'd been starving himself, and AFO didn't like this at all.
With the LOV treating everybody like family, they didn't like when Izuku was unhealthy. Mentally or physically. And since he was struggling with eating, and had an ED, somebody from the league was trusted to stay with him during lunch, breakfast, etc.
After weeks of training, months even, his body was healthy, he was eating healthy and was good in all sorts of skills. Since he was naturally good at analysis, and with how amazing he had become with combat, speed, aim, and even more, AFO himself wasn't even convinced he was quirkless.
The League of Villains were trying their best to become well known to the world. They had sent so many heroes to the emergency room, and they still had only 3 people!
Izuku became known too. No one knew what his quirk was, but they knew his name. All civilians and heroes, and villains, knew his name was Deku. Or at least that was his villain name. Yet again, no one knew what his real name was. He made himself known to the world, with Shigaraki and Kurogiri too, and AFO staying behind in the shadows. The world was afraid of the trio. Shigarki, Kurogiri and Deku were unstoppable. Anyone who managed to get a hit on the amazing Deku himself would be decayed by Shigaraki, and no matter how many times they got caught, Kurogiri would always get them out.
People thought Dekus quirk was analysis, the ability to look at someone and know their quirk, strengths, weaknesses, name, age and personality. Others thought it was Combat Enhancement, the ability to enhance how good he is in one-on-one combat fighting. Or groups. Few thought it was IQ. But none of them were right. He was so good that no one realised he was still quirkless. Even heroes weren't sure. He had already defeated Hawks, Kamui Woods, Midnight, Mirko and got a few hits on Endeavour. He burnt Hawks and Kamui Woods. Midnight was practically quirkless to him because part of his villain suit had a gas mask, so he wouldn't be affected by her Somnambulist. And with her barely having to go into close up fighting, he was very easily able to knock her unconscious and get away. Mirko was a harder person to beat, however. Her amazing skills were admiring for the villain. So much that he uses his legs to kick now, he took inspiration from her rabbit movements and skills. The only reason he was able to defeat her was because she went off guard to speak to Endeavour through an earpiece. He didn't beat Endeavour. He didn't want to. He took a few hits and got bored of his pride. Endeavour wouldn't stop talking about how he was going to defeat his with his 'amazing' prominence burst and how he deserved to be the number one hero. There was a reason he wasn't number one. Civilians didn't like him, he's easy to be scared of.
Eventually, Deku had made the League of Villains known for what it was and got his body prepared for a new quirk in the process. He was a whole new person. He was allowed to choose any three quirks. Izuku wasn't keen on violence. He preferred making other people quit instead of beating them up till they have no choice. Thinking this, he asked for a quirk called 'Spell'. This quirk allows him to have anything he wanted as long as he sang or said a certain spell. He could do it without having to touch anyone, but he had to be holding a book in his hands. It didn't need to be any certain book, it could be any.
The 2 other quirks he chose are Telepathy and Copy. Telepathy allowed him to share his thoughts to anybody around. For example, if he were right in the middle of the UA Sports Festival and he wanted to tell everyone something, every single person in the audience and in the building would here it. Every. Single. Person. Moving on to Copy, it was exactly like Neito Monoma from Class 1Bs quirk but much more advanced. Instead of only being able to use it for 5 minutes and only being able to use it once at a time, he can completely copy anybodies quirk without stealing it from them like AFO. He can also have it for as long as he wants and can use more that one at a time for as long as he likes.
He asked AFO for one more quirk.
"What? Do you not have enough, young man?"
"I do, sensei. And I'm forever grateful for that. However, there is one more quirk I wish to ask for."
"It depends. Izuku, what quirk do you wish for?"
"Genie."