Bitter

Bitter can be made sweet through the masking of taste, as can the sweet be made bitter. This is true, as well, of emotional bitterness.

Veblen asked too many questions, suffered from a constitutional inability to say yes.
Socrates asked questions, drank down the bitter drink one night when the first cock crowed,
but Veblen
drank it in little sips through a long life in the stuffiness of classrooms, the dust of libraries, the staleness of cheap flats such as a poor instructor can afford. He fought the bogy all right, pedantry, routine, timeservers at office desks, trustees, collegepresidents, the plump flunkies of the ruling businessmen, all the good jobs kept for yesmen, never enough money, every broadening hope thwarted. Veblen drank the bitter drink all right.

I like bitter things, grapefruit juice, all of that. Most likely I'm a bitter person, which is why people avoid me – but since I'm bitter, if they didn't avoid me already I'd be wracking my brains trying to figure out how to get them to.
Cyanide, I hear, smells like bitter almonds.

The bitterness of macha, powdered green tea, is perfectly complemented by the sugary nature of tea sweets.

A bunch of my 40-odd year old nightshift co slackers were trying to figure out which parts of their tongues were sensitive to the supposed four main tastes: sweet, sour, bitter, salty. They couldn't think up anything for the bitter category that didn't fit better under sour, so I muttered »alum« into a magazine. Headslapping astonishment ensued. One of them told me I had no business even knowing what alum is and that he could often sense I was an Old Soul.