The Captain America of 2012 stared into his future counterpart's eyes with a determined look. There was only one logical conclusion he could come to:
"I have eyes on Loki. 1st floor."
Steve gently put down the case and calmly explained "I'm not Loki. And I don't wanna hurt you." He was about to explain his complicated situation before the Captain rushed in to subdue this imposter.
The Soldiers out of time began to duel, neither getting the upper hand before the Captain landed a lucky kick to separate them.
"I can do this all day." He declared
"Yeah, I know. I know." Whilst the advanced Stark technology in Steve's uniform helped provide some basic durability, it was no match for his past self's superhuman strength, speed and unyielding nature. The only unique advantage Steve possessed was his knowledge of both the future and his old fighting style, although right now it wasn't providing much help.
Both Rogers' threw their shield's at one another which clanged away harmlessly as they continued to brawl. Eventually the Captain got the upper hand with his punches and kicks becoming more and more brutal. Eventually he socked Steve in his prosthetic Jaw leading to it finally breaking and flying off. This shocked Captain America as he realised, he was looking at his pre-serum self. His blood froze for a millisecond which is all Steve's needed to slip out of his grip and grab the Staff.
Before he could get away, Steve was tackled, and the two soldiers and the staff fell to the ground floor. The artificial legs in Steve's boots finally broke from the damage from the fight as well as absorbing the fall to the ground. And now without his Stark Tech stilts, Steve looked even more like his true self. This confused and freaked Captain America even more before his iron clad resolve took over.
"Your tricks won't work on me Loki"
He was about to attack once more before he noticed a locket of Peggy, one identical to his own. "Where did you get this?" the captain asked. He knew he had to subdue this imposter but so many things just were not making sense.
Steve sensed his confusion and went for the Staff again, nearly getting away before being wrestled into a chokehold. Both men were thinking the exact same thing "This needs to end, now."
As Steve was blacking out, His life was flashing before his eyes, the last bits of advice Antman gave him, his fight against the Hydra soldiers in the elevator, his discovery that Bucky…
"Bucky... is... alive!" Steve choked out in desperation
"What?"
Finally, Steve had the advantage and took the chance to sucker punch his counterpart, grab the sceptre and use it to render Captain America unconscious in one swift move.
Steve choked and coughed and finally caught his breath now that the fight was over. As he gathered the now broken bits of Stark tech that were scattered in the fight, he gazed at his unconscious counterpart and came to one final realisation.
"That is America's ass."