"The best lack all conviction, while the worst/Are full of passionate intensity" - William Butler Yeats
Dunning-Kruger is when someone is incompetent, doesn't know it, but instead thinks they're doing a bang-up job. I have only seen a few cases of it, but by God they cause a lot of trouble.
There is no name for the opposite that I know of - when someone underestimates themselves but does a good job.
I first noticed Dunning-Kruger when I was in college and working as a security guard - although it wasn't called Dunning-Kruger at that time. There was no name for it.
We had a "sergeant" who was always bragging about being in the military and had a blustery attitude. No one liked him, to the point one guard asked him what the current time was in military time.
His answer? "We didn't use it when I was in." A blatent lie and he was clearly never in the military. He was soon removed from his position and rank soon after.
I'm sure this came out of the blue, since he was convinced he was doing a great job.
The worst I ever saw was a middle-aged, scrawny, unattractive woman (who was third choice for the job) who was convinced she was doing gangbusters at her PR job.
She lasted four months before being removed. She was an utter incompetent, but was clueless about how bad she was. And she was stunned when removed.
I have found first-rate people hire first-rate people, second-rate people hire third-raters, and third-raters hire fourth-rate people. When those with Dunning-Kruger get into positions of authority, their castastrophes spread out like circles in a pond.
People with Dunning-Kruger are very confident, but they never have anything to back it up.
On the other hand, people who show humility - which means you know your limitations - are the ones who should be hired. They're the ones I'd hire.
Smart, competent people almost always underestimate themselves. In fact, I'd define a smart person who knows just how ignorant he really is.