The bitterness in coffee (and beer) is an acquired taste. At first it may be hard to take, then one gets used to it and eventually craves the taste. I used to love strong black coffee, and I liked it when there were several flavors present, as in a fine wine. A few years ago, I had a violent attack of nausea. The last thing I'd had was some strong, rather bitter coffee at a function I was attending. I actually liked the coffee, but when I started getting sick later, the acidity of the coffee seemed to make it worse. I didn't drink coffee for weeks after, and when I did, I found I needed cream to tone down the bitterness. I still drink the coffee strong so that the cream does not completely overwhelm the coffee flavor.
I love K-cups because every cup is fresh-brewed cup. There are a gazillion brands, strengths, flavors available. I like Peet's Major Dickason brand.
I’ve never got what I consider ‘strong coffee’ from a K-cup.
Closest is Death Wish K-cups, but not really worth the money for K-cups. By contrast, regular brewed Death Wish is DY-NO-MITE.