He may not always understand, but Hulk knew.
He knew tiny man did not like him. Hulk did not know why, but tiny man did not like him. Tiny man wanted Hulk gone; Hulk had only ever wanted to protect tiny man. Hulk knew when tiny man's pulse went up and when tiny man felt pain, which meant something was wrong and that Hulk needed to come out so that the problem would go away. Tiny man did not like this. Hulk did not want tiny man to be hurting, so Hulk did it anyway.
The red woman was afraid. Hulk did not know why. Tiny man was in pain; Hulk was protecting him. So what was the red woman so afraid of? Why did she want Hulk to go away? What was her life compared to his? Hulk was strong. Hulk could protect tiny man; the red woman's life was such a fragile thing. No, her life was nothing. Hulk's life was the important one when it came to tiny man. He could not help getting angry, not when the red woman suggested that she would be able to help tiny man more than he could.
No-one could protect tiny man more than he could.
He did not want to hurt her, though. He was angry, but tiny man did not want to hurt her and Hulk did not want to upset tiny man by hurting her, so he stormed away instead. You are welcome, tiny man.
But the red woman came after him. She crawled out from where she was safe and stared and Hulk knew that when people dressed like the red woman stared at him, bad things would happen, so he screamed at her. She ran, like he knew she would, because they all ran. Tiny man wanted the red woman unharmed, and the only way Hulk knew to do this was to keep her out of the way. Chasing her seemed like the best option at the time. Hulk knew that she was smart; she would not be hurt.
He did not understand why the yellow man attacked him once he got the red woman out of the way. If the yellow man was attacking Hulk, then the yellow man might attack tiny man. Tiny man was giving no direction now, and Hulk did not know what to do. All he could think was to destroy the yellow man and make him a threat no longer. Tiny man did not have any feelings about the yellow man, from what Hulk could recall, so he set about pulverising the yellow man (whom, he soon learned, was a much more formidable foe than he had expected). The yellow man was strong, he knew—the weapon he held so easily was too heavy for even Hulk to lift. Hulk did not like him, though the fighting was fun.
Then the metal bird came and started spitting the little metal at him. Tiny man was afraid of the little metal, Hulk knew. This meant the metal bird was dangerous. Hulk had to kill the metal bird, or tiny man might be hurt. So, of course, he ripped the metal bird apart, from the inside out.
Hulk could feel tiny man stirring as he fell and tried to tell tiny man that he was safe. He slept.
Tiny man was letting him out. Tiny man did not like Hulk. Tiny man wanted Hulk gone, but now? Now, tiny man liked Hulk and understood Hulk and wanted Hulk to help. Hulk was thrilled.
He was all the more thrilled when his first task was hitting the flying metal worm square in the mouth, protecting tiny man and all of his friends. When the blue man told him to smash, things only seemed like they were getting better. All of these people were around, threatening the safety of his tiny man, and he could finally do his life's goal without people being afraid of him. Protect tiny man. Protect tiny man's friends. Protect tiny man's red metal man—that was almost as important as protecting tiny man. The red metal man was very important.
To say that Hulk was enjoying himself would be quite the understatement.
This all came to a screeching halt as Hulk felt a panic that was not his own leap into his throat, the force of it nearly making him collapse to the ground even as he was pushing himself up. What was the red metal man doing? Going up, up, up, until he disappeared? Why? Tiny man was screaming in his head, making noises that Hulk usually correlated with crippling pain, but now Hulk was already out and he did not know how to help. Where was the red metal man?
With tiny man's terror, Hulk was frozen solid for several seconds. Suddenly, before he knew what was even happening, he found himself sinking his fingers into the brick that made up the closest building pulling himself up, up, up after the red metal man. Even the bad men, the ones he was protecting tiny man from, were horrendously still. The red metal man was gone. The red metal man could not be gone. Tiny man would be hurting if the red metal man was gone. Hulk would not allow it.
It did not seem as though the red metal man would allow tiny man to hurt, either, as he was rocketing back to the ground as soon as the hole in the sky fixed itself.
Tiny man was very loud in his head. The red metal man was going fast. Too fast. There was no fire under his feet for him to be going that fast. No, this was not allowed. Tiny man would break if he fell from that high. Hulk could not protect the red metal man the way he protected tiny man, and the red metal man would surely break as well.
Tiny man told him to jump. He jumped, catapulting himself from tower to tower and hugging the red metal man to his chest in the process, holding tightly to the bricks he landed on even as they gave way beneath his fingers. He needed to get to the ground. The red metal man could not fall from the ground, and now the dangerous men were dangerous no longer. The ground was safe. Tiny man did not want to waste any time, so Hulk simply leapt from where he was and spun himself so that the red metal man would land on top of him, which he imagined would be much less harmful than landing the other way around.
Hulk put the red metal man down and the yellow man pulled off his face. Tony Stark? The red metal man was Tony Stark under his face. Tony Stark did not have his eyes open. The red metal man's chest-light was not on.
Tiny man was crying. Tony Stark made tiny man cry. Protecting Tony Stark was as important as protecting the red metal man (Hulk was coming to realise that they were one and the same, though he was unsure as to whether or not this meant that it was now doubly important to protect them both), but tiny man always came first and now tiny man was crying.
Tony Stark flinched and spoke and looked panicked and invited tiny man to dine on shawarma with him. (Or was it Hulk? Tony Stark always liked Hulk, he was never afraid the way the others were. Hulk liked that.)
Tiny man laughed through his tears.
Tony Stark was important to tiny man, Hulk knew. He was important in the way that Betty, the brown girl, was important to tiny man years ago. Betty made tiny man very happy. Tiny man had loved Betty. Tony Stark and the red metal man make tiny man very, very happy (when they aren't making him very, very sad). Tiny man was coming to love Tony Stark, too.
Hulk did not understand, but he knew.