Enigma
Natasha Romanoff was trained from a young age to cultivate a very specific set of skills in a Russian facility called the Red Room. There she honed the skills that would turn her into a human warrior who continues to stand shoulder-to-shoulder with super soldiers, Asgardians and people in armored suits. However, she eventually eschewed her KGB masters, switched allegiances and began working for the good guys.
Trained by the Best
Exhibiting no super human abilities, the Black Widow boasts ultimate human levels of strength, agility, and stamina. She is extensively trained to near perfection in a variety of fighting styles, such as karate, judo, kung fu, and wrestling, and with all manner of weapons—both traditional and high-tech—combined with her background in gymnastics, acrobatics, and ballet to always accomplish her mission.
She can use a simple handgun just as well as a Chitauri battle staff or even Captain America's shield. Her signature weapons include dual batons, a pair of Glock 26s and the Black Widow’s Bite—bracelets that discharge electricity. Romanoff also displays great skill when it comes to hacking in computers and technological systems to dig for information or regaining control.
Beware Her Bite
Many of the Black Widow's enemies were assigned to her, first by the KGB and then by S.H.I.E.L.D.
In more recent years, though, she assists in taking down Ivan Vanko, Justin Hammer, the Chitauri, HYDRA, Baron Wolfgang von Strucker, and Helmut Zemo among others. And those are just the targets we know about.
Some notable foes include, the Asgardian god of mischief, Loki and Ultron. She proves a formidable opponent to Loki, who assumes that he is able to manipulate her when he recalls her past misdeeds. Instead, it is Natasha who gets the upper hand on him, determining that he plans to release the Hulk as part of his plan. When Ultron captures her, she still undermines him to give the Avengers her location, helping them in their plan to defeat him.
Following the events of the Sokovia Accords and Civil War, Romanoff is later forced to come out of hiding with Steve Rogers and Sam Wilson when Thanos and his followers come to Earth in a quest to gain all six Infinity Stones, which would could instantaneously eliminate half of all life in the Universe with a snap of a finger.
Allies Declassified
Although she was raised to be autonomous and without attachments, the Black Widow has proven herself an exceptional team player.
Fellow agent and Avenger Clint Barton seems to be Natasha Romanoff's best friend. She feels she owes him a debt for the role he played in bringing her over from the KGB, instead of eliminating her as a target. She seems to care for him quite deeply, as she bargains for his release when Loki has him under his control. Also, at first, she is the only Avenger to know the existence of Hawkeye’s family.
The Black Widow is loyal to S.H.I.E.L.D. and Nick Fury before they both realize HYDRA manipulated them. Fury brings Romanoff and Barton in when he activates the Avengers Protocol, putting them side by side with Captain America, Iron Man, Hulk and Thor. She goes on to fight alongside with Scarlet Witch, Vision, Falcon, War Machine, Winter Soldier, Spider-Man, Black Panther, and the Dora Milaje.