The facade of professionalism.
I was very intereseted in this rather unusual position, as it matched my experience very well - and the salary was quite handsome. I took part in all 4 stages of the interview process, which included 2 coding rounds - all for a glorified support position in Central Europe, so quite a bar to pass. That included one interview scheduled for evening hours so that the engineer from the US can participate - who didn't bother to actually show up to the interview.
And I didn't really mind until, after all of the rounds, all I got back instead of the promised feedback was the most generic rejection e-mail sent by neither of the 2(!) recruiters I was in contact with. I also got two separate e-mails, however, asking for my feedback.
So here goes: no respect for the candidate.