A little thought to ponder on:

Why do we kill people, who kill other people, in order to show that killing people is wrong?

As soon as he got out of the portal, he did something that most would judge as out of character. He shakily made his way over the couch and flopped down face first on the couch. Electricity funneled through his veins as he attempted to push it into a dormant state. Eventually, after warring with it for a few minutes, it settled down into its' resting place inside his brain.

Restriction #2: Gray Lightning does not settle down easily once it has tasted combat. It will instinctively want a victim's thoughts to further its' evolution. If the lightning is not provided with thoughts, it will release a backlash with strength comparable with how close it is to evolution. It can occur a minimum of seconds after the denial of food, or a maximum of minutes.

"...It seems to be growing stronger, even without me providing it 'meals' to eat. If it happens in combat, I will most assuredly die. It seems that I must start some kind of pain training regime to get used to operating even under its' influence. I need to reexamine my quirk as well."

He pushed his erratically moving limbs to the forefront of his body and flipped himself around so that he was now laying on his back. It was just in time too, because a moment later both Kurogiri and Shigaraki came through the gate. He couldn't allow himself to show any weakness, especially for this next part. The only real way he could see a way out of this situation - without any punishment - was to use his full arsenal of psychological tricks. Even that was debatable.

'But my decision was on point. If I had stayed there a little longer, I couldn't have guaranteed that none of those students wouldn't have taken a pot shot at me. It's not like All Might would have easily let these two escape either.'

"All Might won after all, huh?"

'First, initiate control over the conversation. I can't let this derail in a fashion unfavorable to me. Nor can I let him get the moral high ground. Once I lose the favor of ethics, he can do anything he wants to me, and my words will have the stigma of a criminal.'

The question threw Shigaraki into an almost uncontrollable rage, with slinking fingers wanting to find a home on his neck. He was already in a bad mood because of their defeat against All Might. H-He was supposed to be getting weaker! How did they lose to a fucking debuffed1 boss? Seeing that bastard's calm and collected face only served to consume his sanity even more. It was only his survival instincts that prevented him from making it into a life or death battle. Secretly, that made him even angrier at both himself and the green-haired villain.

It was a cycle of hatred and all-encompassing rage.

Luckily, Deku knew just enough psychology to flip his perspective (to distract him). As long as there wasn't extensive focus on the fact that he basically bailed on them, he would be in the green. And by the time they thought about it more, it would be too late to bring it up.

"I had a feeling that would happen. Truthfully, I've had doubts about this plan the entire time. It's not implausible that it failed."

'It's not his personal failure, it's the plan that failed. This should tone him down a bit, and set up for the next part.'

"...Doubts? What's wrong with Sensei's plan? Are you questioning Sensei?!"

Flashback:

"It nice to see your enthusiasm, Deku. You are fond of that name, correct?" The green-haired villain simply grunted in reply and didn't bother to correct All for One on the assumption of his 'fondness'. He didn't care what his name was anymore. "Ah, it seems I've gotten off-topic. As I was saying, Deku, your enthusiasm is nice. But the fact remains that you are technically still just a teenager. I will be providing plans for the League of Villains, so you don't have to worry about this aspect in particular."

'This is bad. If I let this out of my grasp... I may be forced in a combatant role (fOrCED tO kIlL sOmEonE liKe hEr aGAin). I won't be able to outmaneuver All for One either. I need to think... Figure out something logical!'

"...I don't want to fail you. As you said, I-I'm just a teenager, but I promise you that I can think! I would probably just be useless if I had to fight... Honestly, the only reason I was able to take those villains down was that I had my quirk and surprise on my side. H-How about we take turns? Y-You make two plans, and I'll make two plans and we'll compare... I'm sorry, that was disrespectful-"

Deku could feel his demonic smile through the screen, despite the fact that it was limited to sound only.

"Why not? I did take you in primarily because of your intelligence after all. I shall take my turn first, then."

End Flashback.

He then took the most logical option, (to him, anyway) and charged straight at Deku with reckless abandon. It was only a portal that Kurogiri hurriedly put in place that prevented Shigaraki from any further reckless actions. After being transported to his side, Shigaraki appeared to want to fly into a rage again, but the look in Kurogiri's eyes prevented him from taking such extremes.

"...Deku, would you mind explaining yourself?"

"Of course, but before I do, I apologize. I have caused you some anguish because of my misleading phrasing."

'Well, I actually purposefully did that, solely to get the opportunity to say sorry. It is an excellent way to improve someone's opinion of you, as well as to stroke some bruised egos. I still didn't expect him to charge at me, though. This is easier than I thought it would be, they're easily letting me string around the conversation however I wish. I won't look a gift horse in the mouth, though.'

"You see, there was nothing wrong with the plan in particular. In fact, it was a pretty genius move. We failed, however, at the information aspect of it. If we had in-depth information on, for example, the force of All Might's punches, the rate at which his stamina is depleted, and the amount of power he can peak at... Well, we could have won. You can think of this operation as not a failure, but a simulation in order to get more data."

The duo seemed to have completely bought them words he had been selling them, as the tension in their frames had been completely released. Shigaraki even had a vaguely pleased facial expression decorating his face (it was a wonder as to what you could express simply with an eye).

And then All for One's voice rang out of the monitor.

"I was thinking of punishing you for leaving the arena ahead of time, but... If you've thought about the situation to that extent, it would be reasonable to assume you have a reason for leaving early as well, correct? I'll listen to your reason, Deku."

'...The big bad has come.'