The debut of Natasha Romanoff paved the way for the introduction of more female heroes in the Marvel Cinematic Universe. Portrayed by Scarlett Johansson, Romanoff first appeared during 2010's Iron Man 2, and she quickly left a mark in the eyes of many MCU fans.
From that point on, Romanoff became an integral part of the franchise, starring in several MCU installments, ultimately leading to her heroic sacrifice during 2019's Avengers: Endgame. The nine-year journey of the female Avenger was anchored by erasing the red on her ledger, and it appears that she was successful in doing so, thanks to her integral role during Endgame.
Still, there are several gaps in the mysterious past of Romanoff that have yet to be addressed, and newly-surfaced evidence seemingly offers more clues about the character's secrets.
ScreenRant unearthed evidence from the recently-released Wakanda Files: A Technological Exploration of the Avengers and Beyond in-canon book that Natasha Romanoff could've used a more lethal setting for the Widow's Bite, but she never opted to use it.
The book revealed that Romanoff was using the lowest setting of the weapon, which emits 40,000-50,000 volts, instead of raising it to a more devastating level (250,000-350,000 vols) that could very easily kill her opponents.
In the book, Shuri mentioned that the side effects of the lowest setting of the Widow's Bite could lead to "weakened or sore muscles, cramping, epidermal burns, temporary nerve damage, and temporary lapses in consciousness" while the highest one will ultimately cause "permanent nerve damage, third-degree subdermal burns, loss of vision, even death."
WHAT THIS MEANS
It appears that there are more MCU secrets that need to be uncovered, and the latest tidbit about Romanoff is a prime example of that. Given Romanoff's past as a Russian spy and her heavy ties to the Red Room, it is not surprising that her famous Widow's Bite will have a lethal setting, but the fascinating part of the reveal is the character's decision to not use that specific level in battle.
It is worth noting that SHIELD did supply Romanoff with her electro-shock weapon, and the lethal setting is already pre-equipped for the weapon. As it is, it would make sense that a deadly setting is planted within the weapon since Romanoff has surely encountered a number of highly-dangerous opponents.
Despite that, Romanoff still didn't choose to go with that setting, further solidifying her heroic turn. Not much is known if other Avengers are aware of this notable tidbit about Romanoff, but it's possible that Clint Barton has been aware due to his strong friendship with Natasha.
Whatever the case, 2021's Black Widow will look to fill in the gaps of Romanoff's secretive past, and there's a chance that the film will address this tidbit about the Widow's Bite. After successfully wiping out the red on her ledger during Endgame, fans will get to witness a different side of Romanoff during Black Widow, providing a more thorough explanation of how the character changed for the better.