3. Official bios, such as from the encyclopedia or the back of an action figure's packaging
4. The lettercolumn
5. The writer him/herself
To me, both fights and non-fight demonstrations of power are "feats," and I treat them equally. The rest is moot to me, though I once cared deeply about writers' input. Nowadays, I only care about what gets published. Not what was "off panel," what was "intended," what the writer was "trying to get across," or what the comic was "supposed to show," etc. That sort of stuff is food for thought and fun to discuss, maybe, but useless. The final product is all that matters, in my opinion, and I do my best to go by that as much as possible when evaluating characters' powers or engaging in fantasy fight debates.