What I’m getting at is, Maria was challenging for “the right reasons”. That is to say, she embodied the best of Dark Souls boss design in terms of adherence to the principles you mention in the article. The Nameless King was a lot tougher than Maria, but for questionable reasons.

I really enjoyed the Ludwig fight, and I found that to be the most difficult in the game. What’s interesting is that speaking of difficulty or challenge alone isn’t terribly meaningful, because everyone will have a different experience there — for example, I know people who found Vicar Amelia much tougher than later Bloodborne bosses (even though I found her relatively easy compared to what came later).