Professor Paradox

Chapter 3: who

...

"It has everything to do with your quirks"
Midoriya said, glancing over to all might.

"allow me to give you all a clear demonstration.

All might.
Throw a punch"
He said, watching the class's expression turn to one of utter disbelief.

All might threw a punch straight for Midoriya, he blocked with his hand.
He didn't even budge from his spot.

"Now, as you can all see, all might is punching me right now yet I am not having a reaction of any sort.

Well that is simply because quirks cannot work on me."
He stated, his hand slightly glowing.

Izuku Midoriya
Quirk: absorption.

Not a single quirk can work on the user,quirks leave no damage or effect whatsoever.
The user can choose to absorb the quirks.
If absorbed, they can resend the input back out.
The user cannot amplify what was absorbed, only the shape and amount may be changed.
It remains with the same power as it would have originally had.
When quirks are absorbed they can remain in the system until the user decides when to release it. There isn't a time limit to how long it may remain nor is there a limit to how many quirks may be absorbed at once.
The quirk also makes the user immortal. 
Absorption activation is evident through a light glow that emits through the user.

Backlash-
The user cannot die ever

Quirks that are absorbed eventually have to get used whether or not the user likes the quirk as the longer it sits in the system, the more difficult it becomes to sleep.

The user can still feel pain,it just doesn't last as long as a regular person's.

Midoriya explained it to his students, breaking it down and going into further details.
"And so that is why none of you stood a chance to begin with.

You're all reliant on your quirks"
He said.

"So wait.
You can't feel the heat from Todoroki's fire?
Or Bakugo's explosions?"
Kirishima asked, genuinely psyched out.

"I can feel the heat from regular fire.
However fire generated from quirks has no effect on me.

In a way, you could say that my quirk is the rejection of quirks.
It's almost as if they don't exist, but I can still absorb them so it's a bit of a paradox."
Midoriya explained.

"what about Tokoyami's dark shadow? And yaoyorozu's objects?
What about Aizawa sensei, his quirk allows him to cancel quirks. Can it cancel yours?"

"having come across similar quirks in the past, dark shadow would phase through me. And Yaoyorozu's objects would either get absorbed or fall through my hands.
Aizawa's quirk also cannot work on me."

"...fall through your hands??"

"I told you it's as if things generated by quirks simply don't exist. "

"that's so cool"

"yes.
Now moving on, from here on out you all need to train to be able to beat me without your quirks.
Because if you use your quirks, you're only wasting your energy and supplying me with weapons.

That is the only way you'll be able to beat Japan's super villains.

The day you can beat me is the day you'll be able to beat anyone. "
Midoriya stated, ending the discussion as Aizawa came in.