Did Bushroot, so I got your Negs covered for ya!
1: sexuality headcanon: I also think he’s heterosexual aromantic. Or at the very least very romance repulsed. I will admit that the thought of him banging Darkwing while drunk DOES amuse me, but I don’t really see it happening.
2: otp: Malicia. Like, again, not romantic in the slightest... but they have great chemistry and I enjoy seeing your character interact with them.
3: brotp: Negaduck/Chainsaw for life.
4: notp: ... I haven’t the slightest idea.
5: first headcanon that pops into my head: The Negaverse didn’t always exist. The incident with the Tronsplitter was what created the Negaverse and the Posiverse. While the universe did pop into existance one day, the characters still had lives. So only Negaduck (and I suppose those that interact with him and met Darkwing) are aware that they are only one of multiple universes.
Also I think he only cares about Nega-Gosalyn to the extent of ownership. Doesn’t mean I’m against reading fics where he actually cares about her, though! I think it’s an interesting read. I just think as a character Negaduck wasn’t meant to be deep, ya know? He’s bad because he likes to be.
6: one way in which I relate to this character: I... don’t, actually. Well, I do get fed up with people’s annoyances, but doesn’t everybody?
7: thing that gives me second hand embarrassment about this character: I still can’t believe he wore a diaper. This is a canon thing that has happened.8: cinnamon roll or problematic fave? He’s the definition of problematic.