Speaking of Clint, it is pretty well known that he is Natasha’s closest relationship. However, in the comics their dynamic didn’t start off well. In Black Widow #10: “Total Recall”, they appeared to be rival assassins. In fact, Natasha’s mission was to bring him in. The movie could portray that as well, and the journey they took to becoming friends and partners as well as becoming two of SHIELD’s top agents. It’s clear that Natasha and Clint had a special bond; he named his youngest after her, and she was willing to sacrifice herself in Avengers: Endgame so he could live the rest of his life with his family. They were essentially each other’s “Ride or Die”. Whether Jeremy Renner makes a surprise cameo in a flashback scene, or Hawkeye gets a mention, having a “Clintasha” moment in the movie would be a nice Easter Egg.
“Welcome Natasha, Daughter of Ivan.”
Fans only got a first name, but that was first mention of Natasha having a direct family line in Avengers: Endgame. With few specific details, it is completely up in the air whether they choose to make Ivan Natasha’s blood father , or her foster father. With her history in the comics being slightly older than the MCU, Black Widow could certainly update the relationship between them, giving it a fresh spin for today’s fans. It would also provide an interesting dynamic not seen in the other 21 movies.
Isaiah Ross, possible relation to Everett Ross in the MCU is unknown, is a lesser known relationship Natasha has that is more prevalent in Black Widow #10: “Total Recall” and Black Widow #13: “Autumn”. How he could be introduced in the movie is he could start of as a typical lawyer, but one day, Natasha’s records from her past could be given to him, and he helps protect her from various dangers, getting caught in the middle unfortunately. He would also be a good friend for her in general; she could confide in him over any troubles she’d have while they watched her Cat, Liho. A relationship like this, a friend that’s “not in the spy business”, could add another layer to how Natasha build her family.
With it being revealed that Black Widow will take place between the events of Civil War and Infinity War, it would make sense that her two most notable partnerships would be Steve and Tony. With Robert Downey Jr. reportedly making a cameo in the movie, Tony could potentially be trying to convince Natasha to return after the events in Civil War in exchange for some sort of immunity. With Tony returning the hopes of Chris Evans making a cameo as Cap are also there. Fans who know the comic book lore, would know that both Steve and Natasha sported the looks of their alternate identities, “Nomad”, and ironically Natasha sported a look similar to her potential foe, “Yelena Belova”, in Infinity War. With these looks, there also may come the mention of what Natasha did with the Secret Avengers.
Other notable partners that Natasha has had through her career are: Daredevil (romantic relationship/partnership in Black Widow #17: Fight The Future). And with Charlie Cox being available, he could appear in a flashback mission of when Natasha could’ve had an undercover mission in Hell’s Kitchen.
Captain Marvel and The Winter Soldier (Bucky Barnes), are two other notable partnerships, but are less likely to appear because Carol Danvers was protecting the galaxy at the time after the events of Captain Marvel, and Bucky was in cryo-sleep in Wakanda, undergoing treatment to remove Hydra programming after the events of Civil War.
Before he was crowned as the new Captain America in Avengers: Endgame, Sam Wilson, formerly known as Falcon, could definitely be a potential partner for Natasha. With having being broken out of the Raft in Civil War, a good mission for the movie could be him going along with Natasha to track terrorist cells using Chitauri weapons to gain control of the world.
As far as a liaison goes when Natasha goes on mission while on the run, she could certainly call Maria Hill. With not much screen time given to her character, and her activity between Age of Ultron and Infinity War completely unknown Natasha could’ve explained the whole situation to Maria, in turn gaining her trust and help with missions while she was on the run.