In Avengers: Age of Ultron we see Tony Stark fight the Hulk using the Hulkbuster armor. The destructive battle apparently ends in

the Hulk being knocked out by Iron Man.

Or something along similar lines. During the fight, Stark wishes a number of times for the Hulk to get knocked out and/or "Go to sleep!"

My question is, how is this possible? As confirmed by the Beyonder, "the Hulk's potential strength has no finite element inside." It's often quoted that "the madder the Hulk gets, the stronger the Hulk gets,"  so how is it possible to knock him out to begin with?

  • 3
    one of the writers/directors/etc whatever noted that this is not the unbeatable Hulk - they didn't want to have movies where all fights go like "people go in, Hulk always wins". This one is weaker, and can be beaten. Helps to keep the suspense
    – Petersaber
    Commented Jul 17, 2015 at 7:22

8 Answers 8


Realistically, he was able to be knocked out because there was no other way to end that scene. However, if we're looking for an explanation in-universe, I can see two possibilities, based on what little we know about The Hulk so far.

Not All That Angry

One option is that he was not really that angry with Tony at the time. Starting with the climax of Avengers, we've seen that Hulk is at least capable of distinguishing enemy targets from friendlies and civilians, and appears to be growing more coherent. It's possible that, even within his artificially induced rage, there was some portion of his mind that "knew" he should be directing that anger towards Scarlet Witch. He may have even recognized Tony as a nominal ally.

It's possible that this tiny bit of doubt was enough to prevent him from growing perpetually angry. He was Hulking out mostly out of instinct: he was sent into a rage so he smashed things. But he wasn't really angry at anyone. Perhaps that was enough of a subtle difference to keep his strength reigned in, enough that

Hulkbuster could knock him unconscious.

Not The Same Hulk

The other possibility is that you're just factually incorrect about his power.

It's well established by now that in the mainstream Marvel (-616) universe, Hulk is essentially unstoppable. The more of a beating he takes, the angrier he gets, and the stronger he gets, with no known limit.

It's not at all established that the Marvel Cinematic Hulk has the same potential. In fact, it would be silly to think they he does, because there would be no more dramatic tension. Hulk shows up to fight, everyone else loses, end of movie.

From his appearances in the three movies thus far, we know he is impervious to "injury". To my knowledge, we've never seem him wounded (bullet bounce off him, etc.), and he survived more than one fall from a plane to solid ground apparently unscathed. However, he does not appear to be completely immune to all damage from a brawl. During both his fight with the Hulkbuster armor, and his fight in The Incredible Hulk against Abomnation, he was clearly being worn down by the amount of a beating he was taking.

In particular, remember that

Banner himself helped build the Hulkbuster armor.

It seems unlikely that he would bother if he didn't think there was at least a possibility that it could contain him. Again, it's unlikely (perhaps impossible) for even the Hulkbuster to injure or kill The Hulk, but that doesn't mean it can't render him harmless long enough to shift back to Banner.

  • 3
    Also, in The Avengers Hulk falls from the Helicarrier, and wakes up as Banner; could he have been knocked out when he hit the floor?
    – Möoz
    Commented May 9, 2015 at 21:40
  • 5
    Though we don't know for sure, that seems most likely. The security guard spoke as if he watched Hulk land and change back into Banner, which wouldn't have happened if Hulk had been awake after he landed.
    – KutuluMike
    Commented May 10, 2015 at 1:21
  • 1
    @MichaelEdenfield It's also worth mentioning that in The Avengers/Avengers Assemble, during the Battle of New York The Hulk is at one point overwhelmed by Chitauri fire power. Commented Jun 11, 2015 at 13:32
  • I've read some Hulk comics, not a ton, but some. Although the upper limit of his power seems infinite, it's finite at any given moment. If you applied enough force before he had time to get madder, you could conceivably knock him out, as long as you do it quickly enough, hence Tony's urgency.
    – DCShannon
    Commented Nov 23, 2015 at 23:00
  • The Chitauri weapons have the Hulk bleeding in The Avengers, if only lightly. Commented Oct 9, 2016 at 17:08

Joss Whedon sort of explains this in the commentary.

We originally shot that he changed back to Banner, and was looking around and seeing what he'd done, but I thought, late in the game, that it would be more effective if the Hulk himself was able to register it and that it became stronger than whatever spell Tony had knocked out of him. The only rule of science I have in Avengers movies is "if somebody is mind-controlling you, then you get hit really hard, then it'll probably end."

Taken with how we see the Hulk looking around at the damage he's done, and seeing how upset everyone is around him, a picture is painted of Hulk no longer being particularly angry; his head is now clear of Wanda's visions, and he is depressed at what he's done. When Tony hits him the final time, he likely almost welcomes being knocked out.


A thing to notice in that scene is just before being knocked out, Banner/Hulk was just getting out of the rage that Scarlet Witch put him in. He began to see and feel the destruction he had just caused.

He was returning to his normal self.

At this point, he could've triggered a transformation, seeing as he wanted to stop the destruction. He was more vulnerable than usual. And we have seen before that such a state can trigger a transformation back to Banner.

So in conclusion, he wasn't all that angry at the moment, and was back to enough of himself that he wanted to stop it. This might've made him a lot less powerful than he was just moments ago.

And he can definitely be knocked out in his normal mood. The fall from the hellicarrier reverted him back, similarly he reverted to Banner in the cave in Incredible Hulk. And even though it's not really canon(?) in The Hulk, he reverts to Banner when Betty confronts him.


Dont forget that the Hulk is sprayed with something as well as discussed in

What did Veronica spray on Hulk in Age of Ultron?

This as well as the physical attacks from the hulkbuster helped to subdue the Hulk

  • After reading another hundred Hulk comics or so, I think this is the right answer. Hulk gets taken out by gasses all the time. The other day I read one where the editor added a joke about how dumb he is that he still hasn't learned to hold his breath.
    – DCShannon
    Commented Aug 14, 2016 at 15:29

Even though the Hulk gets stronger as he gets angrier you have to remember that the Hulk can also be hurt and has been knocked out more then once throughout comics.

When the Hulk broke free of the Scarlet Witch control he saw the destructiveness that he unleashed and became a lot calmer so that made him weaker and thus Iron Man gave him the final blow knocking him out.


There have been times when Banner is able to scathe the barrier between the hulks control. When the hulk looks at the pain and suffering of civilians, this is no doubtedly the hulk and Bruce calming down at least slightly. Before the hulk can become angrier Tony land's that knock out blow


The simple answer is bad writing. It would take a blow of immense force to knock out the Hulk but, based on what we have seen in comics, most recently when he was knocked out by Nova, he would recover within seconds. The best way to defeat the Hulk is to calm him, beautiful woman generally do the trick.


To me, it is fairly obvious that Hulk recognises the scenes in front of him from the 9/11 WTC attacks: collapsing building, people covered in dust etc etc. (Some of the scenes could have come direct from the news reports of the time.) This provided such as shock of recognition and regret to Hulk (partly becuase he caused it) that he started to calm down. It is at THIS point (and not before) that he loses the red from his eyes. This weakens him, and it is then when Iron Man hits him. He just strats to get mad again when he sees guns being cocked. The assumption is (it is not shown) that a sudden blow when he is not very mad would be enough to knock Hulk out.

The 9/11 scenes are like a 'psychological blow' to hulk, if you like.

  • 6
    Wh..... What???
    – Wad Cheber
    Commented Sep 7, 2015 at 15:41
  • If it weren't for strange references to 9/11, this answer would basically agree with a number of the other ones.
    – DCShannon
    Commented Jul 20, 2016 at 0:41

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