Black Widow introduced many new characters to Natasha's story and all of their distinct personalities have better context through Hogwarts houses.
The movie Black Widow was the swan song for Natasha Romanoff, filling in all the gaps in her storylines to finish out her series arc. However, the movie introduced a number of characters into the Marvel Cinematic Universe, and all of them had distinct personalities of their own.
An effective way of analyzing character personalities is by speculating which house they would fit in at Hogwarts from Harry Potter since the traits and mannerisms are brought to focus. The likes of Yelena Belova, Red Guardian, among others, all come out with a better context for fans when their characterizations are applied to this method.
The introduction of Yelena into the series canon also brought in another sibling rivalry to the MCU. Of course, this was more of the friendly variety, with Natasha and Yelena coming across like the Weasleys. Yelena displayed the attributes of a Gryffindor, including courage, loyalty, and sheer nerve.
She also had the Gryffindor knack for getting too high-minded, which led to Yelena overestimating herself. Gryffindors also tend to be very tight with their families, and Yelena was the character who appreciated the makeshift family she had once by continuing to consider them in high regard.
Despite his relatively short onscreen appearance, Rick was one of the better characters in Black Widow due to his loyalty towards Natasha. This makes him out to be a Hufflepuff, as people from this house always have the backs of their friends.
Hufflepuffs also adhere to a strict moral code, with Rick also sticking by Natasha due to his belief in what she did as an Avenger. True to the Hufflepuff nature, he was a giver in personality who didn’t ask for much in return apart from Natasha’s friendship.
While many have felt that a number of things in Black Widow don’t make sense, such as Red Guardian’s imprisonment, his motives align with a Slytherin personality. Alexei was mainly in on the guise of the family for his own benefit, as he expected to be rewarded for stealing S.H.I.E.L.D. intel.
He was also a boastful person in general, tying into how Slytherins like to tout their own success. Red Guardian’s overestimation of his abilities are also traits similar to the Hogwarts house, as he continually jumped into conflict by considering himself to be the best and strongest.
The true identity of Taskmaster wasn't shown as much for her full personality to be known in Black Widow, but it can be made out that the real Antonia was more of a Hufflepuff. This comes down to her not holding Natasha with contempt for causing her to become the Taskmaster, tying into the Hufflepuff trait of being forgiving.
Antonia was also more of a quiet personality who didn’t have any distinct traits, which is another staple of Hufflepuff house as it accepts people with unspectacular but congenial attributes.
Slytherins consider themselves to be right all the time and are willing to go to great lengths to secure their positions. Thaddeus Ross pursued Natasha throughout Black Widow to consolidate his hold on the Avenger even though there was nothing to suggest that Natasha was a villain.
Ross didn’t care about being proven wrong, as he’d made up his mind that he wanted to seize Natasha no matter what. He also had the Slytherin attribute of leadership, commanding absolute authority over his forces and retaining their loyalty.
While she did basically abandon Natasha and Yelena as Alexei did, Melina was far more motherly towards them. She was also keen to make amends with the two and didn’t brag about pulling off the undercover mission as Alexei did.
Due to this, Melina came across as a Hufflepuff, as she wanted everyone to be together once more when the opportunity arose. She didn’t take pride in being a Black Widow and was understanding of the challenges Natasha and Yelena faced, tying in with the Hufflepuff trait of showing empathy for others.
Her appearance in The Falcon and the Winter Soldier served to establish the personality that Valentina has, and Black Widow proved it further. She’s not the kind of person who wants personal glory, which rules her out as a Slytherin, and it’s her smarts that make her a Ravenclaw.
People of this house know how to read others and can use it intelligently to their own benefit. Valentina waited for Natasha’s demise to approach Yelena with the target of Hawkeye, going to show that her intelligence is her main strength.
Another example of a villainous Ravenclaw, Dreykov was a highly intelligent individual who planned out all the Black Widows under his control. Slytherins are known to be cunning on the fly while Ravenclaws use their wits beforehand, with Dreykov already having mapped everything out years in advance.
His planning was such that he had the failsafe of using his pheromones to ensure no Black Widow could hurt him. Dreykov also had the negative attributes of Ravenclaws, in that he was so sure of his intelligence that he underestimated the smartness of others.
Natasha was always driven by her bravery, having faced horrors in the Red Room and beyond, but fighting through these to retain her morality. Gryffindors are also deeply remorseful for when they are in the wrong, and Natasha went the extra mile to fix Antonia’s condition due to her turn as the Taskmaster being her fault.
Gryffindors tend to take all the responsibilities and challenges on their own shoulders, and Natasha did the same when she stood her ground to face Ross in the end by giving her family the time to escape. Finally, she displayed the Gryffindor trait of chivalry when she honored her Avengers friends by leaving to break them out from the Raft prison.
