Superman landed, was slowly walking towards Darth Vader. He knew enough about Darth Vader manipulating doctor to prepare Mr. Farty for transport away from the hospital. Then, this villain did something, that nobody seen him and disappeared with his friend on the edge of life and death. He kidnapped him who knows where, but Superman found this Vader in the middle of the battlefield, his friends were unconscious. But he didn't want to spill blood of the soldiers without purpose, they might be manipulated similarly as the doctor.
Darth Vader knew, that this opponent won't be just a piece of cake. Strength, certainity and anger spread from him. He didn't know, what to expect of this opponent. He didn't knew what to expect. He didn't even know his abilities, but the Force whispered to him to be alerted. But for now, he will not rely on stupid soldier, instead will kill him by himself.
Superman: "So, I finally found you. I know you kidnapped my friend, Batman and Harley. Therefore it is a time for surrended or fight. I advice you the first option!"
Darth Vader didn't speak a word, just gripped the hilt of lightsaber more tightly.