My mother’s computer was hit by one of the ransomware boot sector virus/malware a few years ago. To this day, they have no fix for it, even though the guy behind it is long ago put in jail already.
It took me 8 hours to cobble together enough of her computer’s operating system so that it was usable again without destroying any data, in the hopes (vain it turned out) that a fix would arrive one day.
But even while I was cursing the creator, I was impressed. Not impressed to the point of forgiveness — I won’t let myself cross over that moral line — but in the technical ability alone, I am impressed.