Eh? I’m a bit confused what your grudge against Heaven’s Door is, not that I mind if you don’t want to read it.
You certainly see more to her character in Heaven’s Door (although not much). Compared to the personality she had in Angel Beats, or lack thereof, Kanade feels a lot more believable in Heaven’s Door, even if it’s just through small moments. Shame that you don’t see more of her, but that’s just the nature of the manga.
Even though I agree with Pepe in that the relationship seemed to mostly be a one-sided romance in the anime, I feel that it’s unlikely it will remain that way in the visual novel. I believe it’s intended to be a romantic relationship in the anime and that it didn’t really get enough time to become fleshed out and ended up coming across wrong as a result. Regardless of what the anime intended, though, I’d be shocked if there wasn’t romance between the two of them in the visual novel.
As for my thoughts about Kanade? Well, I don’t have anything to say that others haven’t. She, like most of the Angel Beats cast, has a lot of untapped potential™ and is just dying to have more time to herself. You’d need to make something like, I dunno, a visual novel route dedicated to her to even have the time to do her justice.
So here’s my verdict on her character:
Angel Beats!: 4/10
Heaven’s Door: 6/10
xth Beat: Hype/10