Hulk's intelligence was worse than a child's, and his logic was a complete mess. He acted almost entirely on instinct. This other personality could be extremely violent and preferred communicating with his fists.
So it wasn't easy for Banner to put aside their differences and have a proper conversation.
The whole process consisted of Banner constantly shielding his face while letting Hulk pound him everywhere else. At least they shared the pain, and they shared the injuries, too.
"Hulk, we share the same life now. If you keep hitting me, you're just wasting your strength," Banner tried to explain.
Hulk roared.
"We can discuss working together. If you're willing to talk to me, we can negotiate who gets control of the body."
Hulk roared again.
"What you're doing is pointless. Do you really want us to be trapped in this world together forever?"
Hulk roared once more.
"You damn idiot! Take this!"
Luo Xia watched with a pained expression, especially when Banner gave up trying to defend himself and started brawling with Hulk without any sort of plan. The whole thing had turned into a street fight.
Sure enough, when faced with overwhelming strength, technique didn't matter. A wild flurry of punches was the most powerful move of all. As their anger continued to rise, their fists shook the entire Mirror Dimension, making it grow somewhat unstable.
It was hard to say how long they fought. Time flowed much faster in their spiritual state than it did normally. Banner and Hulk's bodies had shattered countless times, only to reform as they tangled together again.
There was one advantage to fighting yourself: no matter who won, neither side would suffer much spiritual damage. Banner and Hulk were completely symbiotic, and there was no telling them apart in life or death. This