For some reason, Negronis, as well as Aperitif like Aperol or Campari, never taste good in my mouth, and believe me, I've tried so hard to like them, but there's always that strong bitter note on the base of my tongue every time.
I can't manage to like them either, but the frozen version with orange juice is better - maybe that would be your gateway Negroni; also I find them hyper sweet, if that is part of your dislike, the sbagliato - try diluting it with sparkling wine or sparkling water.
Campari I do like as an ingredient in fruity drinks, it is so good in lighter drinks, that bitterness is welcome. And I love mustard greens, horseradish, grapefruit, it's not a problem with bitter, it's bitter and so sweet I find off-putting.
I don't mind all kinds of mustards (including wasabi). Fresh grapefruit taste okay, but the longer they sit the more bitter it gets for me. I also like dark chocolate up to 75%.
Not generally. I drink my coffee black on daily basis. Tho more leaning toward the light roast arabica, I could take dark roasts as well as robusta with no issue. I also have no issue with other liquors and spirits.