I may always reblog every gifset/imageset I see of this scene, if only to point out (over and over and over again) that Black Widow’s “very specific skillset” is not, actually, ass-kicking (as amazing as she is at that), because all the Avengers can kick ass to a pretty high degree. The Black Widow’s superpower (as it were) is emotional manipulation.
She is not interrogating this man not while tied to a chair. She is tied to a chair because that is exactly where she wants to be, because apparent vulnerability on her part is part of her interrogation. She uses the exact same trick on Loki later, when she leads him into gloating over having successfully pushed her buttons (and I have a theory that he did actually push her buttons, that she was genuinely distressed by the things he said to her because Loki is old enough and smart enough to know when someone is lying to him) and turns his gloating around on him, uses it to dig into the cracks of him, because that is what she does, and she can do it even when her target is expecting it. (Really, Loki knows that’s why she’s there. He was expecting to be physically tortured first, and for her to come be sympathetic later, if you recall, but Loki and Widow both know that wouldn’t work.)
And this is why she’s so unsettled by the Hulk. The Black Widow relies on emotional manipulation — and the Hulk, to the best of her knowledge, only has varying shades of a single emotion: anger. She doesn’t know how to manipulate a creature if it doesn’t have all the hooks to emotions like pride and lust and guilt and greed that she’s used to using.