1. From what little I know of her, Black Alice, who can apparently become anyone who uses, receives, or has the ability to manipulate, magical energy, however that is defined in DCU, up to and including the Spectre, who is more powerful than any of the heroes people traditionally name in this type of thread.
2. My reflexive answer at the moment is Spider-man. Very few heroes have been, historically, so comparatively vulnerable, so much yearning to live a better life, yet so willing to lay it all on the line to preserve the lives of others.
3. Spider-man. He became my favorite almost from the moment I saw his Secret Wars Action Figure on TV as a little kid.
I thought #2 was an assessment of their character in regards to being a superhero, not just in general.
If that's the case, then I'd change my choice for #2 to Banner (during FOTH)... pawning Doom twice and outthinking Reed on multiple occasions is a character trait.
Oh, maybe I interpreted it wrong. I didn't judge based on character in regards to being a superhero because you can't really top Supes or Spidey imo, so I assumed it was simply depth of character *shrug*
Cap is pretty impressive, but, in the scene you're showing with Thanos, he doesn't really think he's going to die -- the heroes actually have a plan in mind, and that's just part of a ruse.
No doubt Cap would be willing to lay his life on the line just as he says, but, it nearly always strikes me that he, and most other superheroes, get to take a slightly easier route than Spidey, who actually IS in danger of being beaten to death in many cases, and nearly always facing the odds alone. Cap has the Avengers, Superman has the Justice League.
Spider-man, for the most part, does not HAVE the reassurance of allies when he risks his life, it is him alone, only his own skill and resourcefulness and determination, and more than a little bit of luck promising to see him through to another day...
Spider-man has motivations that people can understand and relate to.
Truth, justice, and the American Way? How many people TRULY understand what those concepts mean nowadays?
Yet nearly everyone can understand a feeling of responsibility to do what you can,
nearly everyone can understand concern for friends and family,
nearly everyone can understand an innate desire to preserve life and help those in need, regardless of circumstances ...