Bitter? Hmm I'm pretty sensitive to bitter tastes, but I wouldn't call peanut butter bitter 🤔 it's only bitter to me if the peanuts were roasted too much or the oil has gone rancid. Are you sure the peanut butter was still alright?? It should really just taste like smooth, oily peanut.

I think any nut butter is nice with or without sugar, but yeah, with sugar I'd call it something like peanut spread, not butter.