Warning: contains spoilers for Captain America Annual #1!
Black Widow famously has no special powers aside from her sharp intuition and training as a spy, but Marvel has all but confirmed that Natasha Romanoff has a new superhuman ability: speed. In pursuing a foe with the ability to stop or slow time, Black Widow can not only catch up to him but stop him in his tracks altogether.
After so many years devoted to Black Widow's heroic exploits, it is difficult to remember that she was once a villain. Debuting in Tales of Suspense #52 in 1964, Natalia Alianovna Romanova was - at the time - another Soviet villain in American comics, destined to fail against her capitalist enemies (namely, Iron Man). She eventually became a hero in the comics, even joining the Avengers and other superhero teams. For most of her comic history, her past was a mystery - all that was known was that she was trained as an elite spy and, if necessary, assassin by the USSR's shadowy Black Widow Program. In many ways, her horrific training in the notorious Red Room still haunts her.
In Captain America Annual #1, by Gerry Duggan, Marco Castiello, and Ruth Redmond, Black Widow joins Captain America in the hunt for Hector Bautista, aka Overtime. On the run after escaping death row, Overtime has since been chosen by the Time Stone as one of the six Infinity People to bear the Time Stone. Since he holds some of the Time Stone's power, he also holds some control over slowing and even stopping time (at least from an outside observer). When caught, Overtime uses his power to make a quick getaway...only to come face-to-face with Natasha.
"She's fast," observes Overtime - which is quite a magnificent exaggeration, considering Black Widow essentially surprised a man who can slow time to a standstill. Black Widow may appear to be an average human, but she actually does have some low-level superhuman abilities; the USSR gave Natasha their own version of the Super-Soldier Serum, which gave her peak human abilities. Thus she may have superhuman speed, strength, and agility, but moving at speeds equal to the Flash is a new ability for her. Except it's not: in Heroes Reborn: Siege Society #1, Black Widow is shown reacting faster than Blur, Marvel's pastiche of the Flash.
This issue, along with Heroes Reborn: Siege Society #1, raises two possibilities. Either Black Widow does indeed have super-speed abilities that rival a time-stopper, or (more likely) her ability to predict her opponents' movements are so acute, they can outfox even a speedster. Twice in recent comics history, she's been able to get the drop on characters a great deal faster than her: proof of Black Widow's superior training in the Red Room, skill, and ultimately determination.