Destroy, exterminate, murder.
That's what his inner voice kept telling him. The voice that appeared after his brush with death, after his body had changed and the new energy started coursing through his veins. That's all it ever told him to do.
Destroy
He didn't want this. He wanted to live in peace, away from humanity. But the inner voice beckoned him. Filled with enmity, it commanded him to murder the human's brothers, sisters, and children. No matter how much he tried to resist, he couldn't fight it. No matter what he did, it wouldn't go away. Whenever he fought it, it sent a great, great pain through his brain. Fighting it was like going against the will of his very soul. The rage would never go away, it would never let him live in peace. He could only do what he had come to loathe.
Destroy
He walked through the human city known as Tokyo, explosions marking his trek through it. Weather there were any humans remaining or not, it didn't matter to his inner voice. It wanted only destruction, to destroy what humanity had created. To destroy this great beauty, they had built. To destroy the utopia they had achieved. As he walked through the city, something made him stop. He turned to see what had garnered his attention. Inside one of the skyscrapers, was a lone human. He didn't seem fazed by Godzilla's presence. It was like he welcomed it. The monster king's eyes squinted in recognition. He remembered. This was the same human from all those years ago. The human who he had saved. The human who looked at him with respect and honor. The human who praised him. The first being he ever considered a friend. The human remembered him as well.
Destroy
He couldn't do it, he just couldn't kill the only friend he had in this world. He was alone, so very alone. Only the voice kept him company. The voice he despised with all his heart.
Destroy
He had to fight it. He couldn't let it win this time. If he did, then it would always be this way, always with the rage and hatred that was forced upon him. Always forced to murder the innocent.
Destroy
No, he can't. He mustn't.
Destroy
He had to be strong; he had to protect his friend. The pain from fighting grew and grew. Godzilla closed his eyes in concentration, trying to cast out the voice. It was growing stronger.
Destroy
No, not this time. This time he had to break free. He had to fight it.
KILL!
It was no use. It was just too strong. He opened his eyes. Deep within them was a great sorrow. He reared his head back and roared. It wasn't a roar of challenge, or of anger. It wasn't a roar of rage and hatred. It was a roar that begged for forgiveness. Then he fired his atomic breath, destroying the only thing he had left in this world. The top of the building exploded, sending chunks of debris everywhere.
ANIHILATE!
He tore through what was left, leaving nothing but rubble and ashes in his wake. As he walked away from the remains of Shindo's tower, a single tear rolled down his cheek.
Forgive me, old friend.