I have busted one checkride in my entire life. It was my ATR-42 type ride, and the Director of Training for the commuter I worked at was the DE. I had already been a Capt there in the DCH-7 and the J-31 for 4 years, and of the three, the ATR was by far the least labor intensive to fly. I had a company instructor in the right seat that was also getting typed.
The ride was going great, one of the best in my career. I was banging out emergency procedures and approaches like a machine. He then had me do a single engine, circle to land NDB (multiple emergency?). Everything was perfect, until I started base to final turn (arguably, I was in position to land), where I dipped about 60' low (I was looking "out" the side windows in the sim, which is VERY disorienting) and the F.O. said "altitude". I corrected, then about 3 seconds later, started my descent to land.
I did the rest of my ride without a hitch, and, feeling pretty good about my performance, went into the debrief room, where Mr. DE aksed me for my certificate. I jokingly stated to him to make sure he got the spelling right on the temp. He said "you mean the pink slip". I laughed and then saw that he was serious. He told me that there was no way that he could possibly pass me, since my performance was so bad! I really thought he was joking. I asked where the deficiencies were, and he said the NDB, and also said that my tracking on a single engine ILS was a bit "unstable" (I landed out of it at minimums.... he was using the printout fom the sim to base his judgement. The initial localizer tracking from the almost 90 degree intercept, with a 20 kt crosswind was a little shaky, but was completely stable before 1000'). That was it. A BUST on my flawless training record for those 2 INSIGNIFICANT "errors".....
There was still about 45 minutes in my turn of the sim session, so I asked if we could just go in and redo the 2 "deficient" maneuvers, and he refused.
The guy I was with couldn't believe that I busted, as he had been my training partner, and he even said that the ride was the best he'd seen me fly the thing. As an aside, I run into him every so often, and he usually brings up how I got F***ed on that ride.
I still had to fly the right seat for the other guy, who made a lot of mistakes and still passed (he even said before we went into his debrief that he thought he failed).
I was pissed. I will accept responsibility for my actions, but this was ridiculous.
I had to do some remedial ATR ground training and then redo the ENTIRE ride again, with the same guy (only ATR DE available!). I called the chief pilot and pitched a fit, and found out that Mr. DE failed 60% (!) of the guys transitioning from the DHC-7 and J-31 on their ATR type rides. The feds almost made us do outside training, since we obviously weren't being trained well enough with this kind of failure rate! At my request, I had an ALPA rep in the JS, the chief pilot in the right seat, and almost had the POI there as well for my make up ride. The DE was more nervous than I was, and even though I screwed up more stuff on the second one, now that I had witnesses, I passed with a pat on my back, and a "Great job!.....Much better"

from the DE.
The guy was such a jerk, that he had a hard time doing checkrides, because people would call in sick for their PC's when they had him.
We found out much later (from a FA who'd been there) that he suffers from SPS (small p*nis syndrome). He will NEVER get a real job, as there are so many of his former victims at the majors and cargo outfits to make sure of it.
He is now running for congress.