How would you rank Black Widow’s friendship with each Avenger?

The ranking is from 1(weakest friendship) to 10(strongest friendship).

Quicksilver: 1

Because there wasn't much of a friendship between Quicksilver and Natasha, I'm awarding him a one.

This is the finest photo of them I could find.

Clint Barton's son's names are Nathaniel (after Natasha) and Pietro (after Pietro), which is incredibly sweet.

Captain Marvel: 2

It was a missed opportunity for Captain Marvel and Nat to form a strong friendship.

But I'm sure they'd have made excellent buddies.

Rocket Racoon: 2

They weren't actually buddies; rather, they were teammates.

Bucky Barnes: 3 (IDK if he counts but he’s on the list)

Bucky and Natasha were more than just adversaries. They had a lot of fights. They're a pair in the comics. I came across this meme which shows what would have happened if they were dating in the MCU as well.

They just fought a lot (like I wanna kill u fight)

Nebula: 3

They worked together and shared many characteristics, so they would have been wonderful buddies.

Scott Lang: 3.5

they fight

and they talk and seem like friends.

Vision: 4.5

Nat and Vision don't appear to be the best of friends, yet they've been comrades for a long time and both supported Iron Man.

Okoye: 5

Okoye and Black Widow are both incredible and fearless women who work well together. However, we never got to see how their friendship progressed.

War Machine: 5

For a long time, War Machine has been Black Widow's friend. They were both members of Iron Man's team.

Scarlet Witch: 6

    Scarlet Witch and Black Widow began as foes but quickly became friends, they even worked together for several years after Age of Ultron.

Thor: 7

Thor is the OG Avenger Nat has the least of a relationship with, I don't recall Black Widow and Thor ever having a full-fledged chat. And, as far as I recall, they never had a one-on-one in front of the camera.

That’s their most famous scene

Falcon: 7.5

In Winter Soldier, Black Widow and Falcon frequently collaborate and are strong friends, After Civil War, both are in exile with Cap for 2 years which must have strengthened their bond.

Iron Man: 8

Due to Stark's ego and weak teamwork abilities, their relationship is difficult. Tony enjoys being the center of attention and being the loudest person in the room. Natasha is a secret agent who prefers to carry out covert operations and observe from the shadows. They take a completely different attitude to things. It was amusing how he went insane at the sight of her (earning Potts a lot of jealousy) and then found out who she really was. Am not even sure what was the real reason for Black Widow choosing Iron Man's side.

Bruce Banner: 8.5

Truthfully speaking no one likes them romantically being involved and it was also pretty awkward seeing them talk about, how they both can't have children ........

They both know how much they want to be decent and redeem themselves, and how much they despise the monster within, they were really really good friends, but for the whole awkward relationship they deserve an 8.5

Hawkeye: 9.5

Among the Avengers, Natasha has the longest connection with Hawkeye. Perfect brother-sister relationship I'm not sure I've ever seen one. She was always grateful to him; the life she adores is only possible because he made a different decision years ago. They were the quintessential best friend duo. The female and male versions of the same individual. The most intense form of platonic love.

Natasha became so close to Barton that she is one of the only people alive who knows about his family, and Clint's new child is named after her (Nathaniel being a masculine version of Natasha). It would have been number one if we had seen more of their relationship onscreen instead of constantly hearing references to Budapest. Clint and Natasha spend so little screen time together that we have to be informed they are quite close.

Captain America: 10

Nat and Steve are two sides of the same coin. Two very different people who find solace in each other. Partners at their best. He exemplifies what it means to be a good man: he's honest and fights for what's right. She's a spy who fights according to an agenda. His goodness was a source of inspiration for her. And in some ways, he looks up to her.  

Unlike Clint's and Nat's virtual relation, Steve's and Natasha's relationship grew from the moment they first met. Natasha and Clint each said one sentence to each other in Captain America: Civil War, but Steve and Natasha's bond was evident throughout the film, from Natasha comforting Steve after losing Peggy to Natasha assisting Steve and Bucky in escaping. At the end of Black Widow, Natasha claims that she is going to help her family, which is Steve. Theirs was a relation which literally every MCU Fan wanted to see turn romantic. It was Marvel’s fault, they had too much chemistry. They always hug, kiss, and shove each other against the wall, they act like perfect couples, even their expressions towards each other throughout are so awesome. If you look closely we can see Natasha always loved Steve, he was just too dumb to understand it. Both trusted each other to death.