More than a decade ago and when I first began my website, I had a DE visitor that was denied.
They apparently didn't like the door being closed and set about of the next 4-5 hours (while I was snoozing) eating consecutive 403's.
I never counted how many, it had to be in the thousands.
Not sure if they believed they could crash the server or was just throwing a fit ;)
BTW, they occasionally caught a 200, however were going so fast with the requests that they never saw the 200.