Being the only girl in the team had ups and downs. She is known to be more badass (which really boasts her ego), but she has more spotlight. As a spy and assassin, she never was allowed to have any feelings. Missions could be compromised because of feelings, so it was after a long time was she able to have feelings.
Spotlight is something Natasha should not have, especially on her relationship status. Being the only girl in the team, it isn't really a surprise that people begin to wonder about her romantic relationship with boys. Especially if you live with six attractive men.
Tony and Thor were obviously excluded from the list of potential boyfriends considering the fact that they both are open about their relationships. Though some people believe that Tony is cheating on Pepper with Natasha (Pepper was cool about that rumor, only God knows how much rumors she had known).
Clint was the obvious one, or so their fans and people say. Clint is the one who knows Natasha the longest, and whenever on a mission, they are always seem together. Hell, even some agents from SHIELD had betted on them the fact they were sleeping with each other. It was to the point that even Fury had asked them, but neither confirmed or denied the rumor. The rumor was so popular that even their enemies knew about it, but they said nothing. It was easier for the ordinary woman that Clint loves because the Black Widow would be used to get to Hawkeye, and the Black Widow is more feared than scared.
But Natasha knew that there couldn't be more than friendship with Clint. Yes, he was the one that she had spent more time than any other member, but that necessarily mean that they were romantically involved. He had saved her from hell, brought some good out of her. What they have between wasn't the love you expect from a couple but from a family. Clint is the first one to see her more than an assassin, and the first person close enough to be her family. They had their ups and downs, but they couldn't be what others expected them to be. They had a mutual understanding of what they were to each other: a family. So definitely Clint was out from the romantic list.
Steve Rogers came next. The super soldier, many girls deem him to be the perfect guy. Handsome, tall, strong, and incredibly polite, Steve didn't even need to do anything to have girls fall for him. Maybe if Natasha had a normal life and didn't know Steve like the normal girls, maybe she would have fallen for him too. But she is the Black Widow, and nothing is ever normal for her. The Steve she knows is broken just like her, but in a different way. He is lost and in a time where he doesn't belong. But he can get adjusted, and try to start a new life (if he gets over his shyness, maybe with Maria).
Steve and Natasha are polar opposite of each other, and she will never understand him because of it. There was no way they could be in a relationship, in her opinion. He was too good for her, and she had too much of blood in her hands. He would never understand her for what she could do. Maybe if she wasn't programmed to survive, even if it mean to kill, and he was gifted to protect others, even if it meant to get killed.
They could never understand each other, but they had a loyal friendship, which was fun at times.
The least famous "OTP" of hers is with Bruce. There was no way that they could be together. No offense to the Bruce fans, but shouldn't Natasha be with someone like her? Clint and Steve are soldiers like her, while Bruce is a civilian. He is a gamma radiation specialist while she is an assassin. They are world apart and there is no way they are together, or so the fans say, Natasha thought as she looked through a social website called tumblr (she'll definitely keep the site in mind, potential Intel available).
While her fans may be right, Natasha thought, they don't know the true story. But a particular post caught her eye as she scrolled through her tag (Tony would probably already know what his fans think and might not be able to figure out why he is paired with Steve, even with his genius mind).
"I don't really need to get any hate for thinking that Bruce and Natasha might be together, first of all. But, I do understand why people would think this is weird. In our point of view, Bruce and Natasha are totally from each other and how could it work out with the Hulk and all, but it makes sense to me. I can see them both together, not as superheroes but normal people. Before the Battle of New York, the Hulk were feared, and people knew them as monster. The Black Widow did not have the cleanest record, and by enemies and allies, she was known as a monster. Both had been uncontrollable and deadly, but we always forget that they are humans too. I see as the Hulk as the alter ego of Bruce, and it is his way of protecting himself and keeping Bruce safe. The Black Widow made Natasha to survive anything and protect themselves. Their situation to survive and protect did lead them to do something they never wished they had done. To repent for those choices, they try to protect the innocent, either while hiding or killing the bad guys. While Clint is too in the same position of Natasha, did he have to kill and train at a really young age? He might understand it, but would he know the feeling to kill one of the girl you thought was your sister to survive? Would Steve understand the feeling the reason to protect innocent lives is because to repent for your mistakes?"
"We are so into judging others for what they did that we forget that those people have feelings too. We only glorify the mistakes they did rather than appreciate their good deeds, and we forget that superheroes are humans too. Bruce and Natasha knows what it feels like to be at the other side of our judgement. They know how it feels like isolated from others to protect them. For one to not fall back as the monster seen by people, the other can only help if he knows what it truly feels like. Bruce and Natasha are connected in a way we might not understand, but that doesn't make it unthinkable."
"And maybe I am wrong. Maybe it is something. We only know them as the Hulk and the Black Widow, not as Bruce Banner and Natasha Romanova. We don't truly know who they are, but they sure can date who ever they want."
Huh, Natasha thought. That was interesting.
"What are you reading?"
She looked up to see Bruce coming towards her. She let a small smile out, and watched the same action on his face. "Nothing," she murmured as he pressed his lips on hers.
Okay so that was my opinion on the couple. A lot of people are saying why can't Natasha just not have a love life, but I feel like that would be a big mistake because falling in love is a normal thing. By showing that she doesn't experience something that humans would make it difficult for me to connect with her. For me, she is an ideal example of no matter what happened in your life, you can do something about it and be good. That is who a superhero is in my opinion, and anyone can become a superhero. Natasha does feel love, she just interprets it differently.
Btw, I feel like the scene of Brutasha from the trailer is something that happens in Bruce's mind while being control and the experience pushes them to acknowledge their feelings.