Time Variant Assassin (Alternate MCU Story)

With the Captain

David and Steve were on their way back to wherever Steve took them. "You're a helluva fighter. None of them were left alive." Steve said to David.
"Well, I'm an assassin. I kill the bad and end the suffering." David told Steve.
"What happened to you to turn into an assassin?" Steve asked.
"Whats makes you think something happened?" David retored.
"I... can just tell." Steve added. Davis sighed and looked around. "There was another Captain America." David told Steve. It was a lie. David had to string together a line of lies to tell Steve. He didn't know what could happen if he changed the past too much. "The other Captain America... he died while going on his mission." David told him. "And it lead to the opposing side winning. They took my wife and child. They're dead." While it was a half truth, David felt like he was somewhat opening up to Steve. Then he came up with another complete lie. "I'm not as young as i look. I took a serum to slow my aging. I'll die one day, but it won't be tomorrow."
"I'm sorry, David." Steve said.
"Steve... I don't care why I was sent here. But heres what I say: I need to make sure you do your final mission when it comes. It may be cold, but if you don't do it, millions will die." David told him.
"I will. I won't let my country down." Steve said.
"Whatever it takes." David said. "Just know I may not be alive when you return from it."
"Okay." Steve said. We kept walking. David knows he can't stay there. He needs to return to his own universe and the TVA to tell Paradox to fuck off. Then David and Steve got shot at. "Shit! Get down!" David yelled. Steve held his shield up and they ran. David started shooting back until they got behind cover. "Let me see if I can see them." I said. "Give me your shield." Steve handed David the shield and David looked over the rocks. He saw five people. He ducked back down. "You see them?" Steve agreed
"Yeah." David told him. He jumped up and shot at them. He hit three of them. He went back down. "Two left." David told Steve. He went back up and shit again. Click click. Empty. David got shot in the shoulder and went down. "Fuck!" David yelled. Steve took the gun. David handed him a new clip and reloaded it. Steve shot at the last two guys and killed them. More came. "Go, Steve!" David yelled. "I'll hold them off."
"Not happening, you need-"
"GO, YOU BRAVE FUCK! GO!" David shouted. Steve ran. David shot back and killed some of them. Then he opened the portal and went through without knowing where he was going.