You had been kidnapped by Hydra as a baby, and trained to fight from a very young age. When you were old enough, they gave you powers. They decided to make you their most powerful weapon, and were now on your first couple of missions. You’d taken out a few politicians, under Hydra’s orders, and were now in the UK, targeting royalty. You were mind-controlled, so had no idea what devastation and chaos you were causing.
You were aiming down the sites of your sniper, finger on the trigger, ready to pull. You were sat in a hotel room, waiting for the right moment to strike; the moment you’d put a bullet in the King’s head. The hood of your cropped hoodie was up, concealing your face almost completely. You had a mask on that covered your mouth and nose, leaving only the strip of skin around your eyes visible.
You saw something red white and blue out of the corner of your eye. A circular shield. Before he could lunge at you, you’d pulled the trigger, just as you were tackled to the floor by Captain America. It was too late.
The rest of the Avengers came out from their hiding spots, knowing that the bullet had already been fired, they were now focused on bringing you in.