Black Widow- 8
I did notice the editing in action scenes, but it didn't prevent me from following what was happening so want really bothered. The scenes themselves had cool stunts, and good fight choreography so I enjoyed them overall.
Then there's Taskmaster.
They gutted one of the avengers more charismatic villains, and turned him into a robotic, silent stalker. What kills me is the film didn't even need this. There was already enough drama with Widow's dysfunctional "family". It didn't need this extra bit, at the cost of ditching one of the more fun villain personalities in the comics. That said, they nailed the characters powers and abilities. Very much enjoyed all of Taskmasters fight scenes.
Also, yeah, Yelena was great. If the eventual plan is for her to take Natasha's spot, she couldn't have had a better debut, to get people invested in the character.