Marvel x pacific rim: Steve Rogers01

Steve Rogers always wanted to look out for the little guy. Unfortunately, he was the little guy. Luckily for him, his lifelong friend James Buchanan Barnes, AKA Bucky, was there to back him up. But when the Kaiju attacked, all of humanity was the little guy. When DARPA Tech's neural interface for fighter jets was shown to be an asset after Brawler Yukon brought down the Kaiju Karloff, the Pan Pacific Defense Corps pumped out much propaganda in hopes of finding drift-compatible pilots. Steve was first in line at the recruitment office, but he couldn't pass basic physical requirements, as the strain of piloting a gigantic robot is fairly intensive. Each year, more pilots would fall, and each year, Steve Rogers would step up hoping to get a chance to look out for humanity, the little guy. But each year, he was still turned down. He was especially dejected when Bucky was able to enter the program, but still, was happy for his friend.

Luckily Dr. Abraham Erskine, who had been researching Kaiju since day one, saw in Rogers a great man, and immediately contacted the top brass of the PPDC. While reluctant, they agreed on one term. Dr. Erskine had to find a Marshall willing to take such a risk for their Shatterdome. Only Marshal Nick Fury, who planned the Avengers Initiative in the interest of playing search and destroy to shut down the Breach, agreed. The good doctor labored many months to develop a serum from the kaiju samples he could get in the hopes to allow Steve to be able to handle the strain of piloting. Luckily, the procedure was a success, especially with the help of Howard Stark, who lent his facility to conduct the procedure. Steve was sent to a hospital to recover, but this is what ultimately saved him, as not long after, a Kaiju made land at the Malibu plant. Dr. Erskine and all hopes of creating more serum were lost as he selflessly stayed to evacuate. The Kaiju, codenamed "Assassin" would have gotten to the hospital where Rogers was held, likely due to the Kaiju derived serum coursing through his veins, if it weren't for the timely arrival of the nearest Jaeger, the American Dream, piloted by none other than Bucky. After recovering, Steve joined the Avengers Initiative, and soon found he and Bucky were drift compatible. Bucky, who's copilot had been injured, was glad to have a copilot to get the American Dream back up to fighting shape. 

She received modifications when Anthony Stark arrived at the program, using his family funds and mechanical genius to overhaul the program's available Jaegers, and even though she was an old Jaeger, Bucky's military background and Steve's tenacity make sure she's one of the toughest Jaegers out there, already having landed five kills.