Just about any time somebody does better than Andrew Younghusband.
Sean did the same thing in the offroad challenge in Season 2 (complete with re-hooking the car battery after it got loose from Colin's run)
In Season Five, Jakob completed the Gimble challenge faster than Andrew.
Dean from Season 6 outperformed Andrew in the Trailer Challenge.
And Paul (also from Season 6) was one of only two contestants to pass the teeter-totter challenge and almost completed it as fast as Andrew did.
From Season 1, David having his nominator clear snow from a mogul while he gets the car started is a great ending to his stay at the rehab center.
Arun from Season 5 became the first person ever to complete the final road test without making a single ticketable offense. Considering how much he struggled early on this season, it shows that the rehab system really works, and got a round of applause from the experts. Even better, Cam, who almost gave up hope for him, calls him the "most improved driver he's ever seen" since he's been on the show.
1. Scott's nominator Danny, after seeing Scott laugh off another failure, blows up in his face and cancels his insurance policy that they both use note Scott's insurance would have been in the $500,000, but Scott was under Danny's plan so he wouldn't pay that much meaning Scott can't continue doing challenges uninsured
2. When Scott goes up to the panel, he asks for them to send him another nominator and using that person's insurance, but is turned down by them.
Diane from Season 8 would pull off a perfect drive years later, with Andrew calling it the best road test he's ever seen.
Aaron's public drive from Season Seven, which was almost perfect (aside from rolling through a stop sign early in the drive). Seeing him grinning from ear to ear as he drives as a normal driver for the first time since nearly being killed by a woman who failed to observe a stop sign was truly a magnificent sight.
Chris Ferguson, the "winner" of Season 1, returns in Ever to perform a nearly flawless performance in the assessment challenge (The only mistake he made was a low-speed collision in the U-Turn section). He ends up being the first graduate of that season. Hell, he's the first person in the entire series to graduate on the first episode.
Remember Shirley from Season 7, who was unfortunately the "winner" of that season? She returns in the Ever Season as well, and showed how much she had improved over the offseason (which included taking private driving lessons in Halifax) and nearly passed every challenge. As an added bonus, she improved her score on the road signs quiz and scored an 8/10. All of that culminated in her being the second person to graduate that season.
One of the final challenges on the Ever season finale was to reverse down a narrow pathway lined with cars, do a reverse slalom, turn around, then Do It Again Forwards. Kevin somehow manages to pass it flawlessly. It's unfortunate that the same couldn't be said of anything else he did...
When Kevin writes a second insincere apology letter in Ever, after yet another epic failure - Andrew and the panel openly scoff at his antics and call him out on his hypocrisy.
A minor one, but Sly's near-perfect road test in Ever saves him from the disgrace of "winning" the trophy.
Thomas' performance in Season 3. Nailed every challenge eventually, graduating second, then winning the first race he entered. Certified Badass Driver.
In the Season 10 premiere, Mariah admits to being a drunk driver. She proceeds to laugh it off in the confession cam and then when she arrives at the rehab center, she makes a further lighthearted comment about her drunk-driving. Andrew then proceeds to thoroughly chew her out, citing that many people who are watching this have had friends or family die on the roads. It's somewhat satisfying to watch the wind being taken out of her sails a bit.
Mariah would later earn herself a legitimate moment of awesome by graduating in the third-last episode, and then immediately getting a tattoo to remind her never to drink and drive again. On top of that, in a scene that was sadly deleted from the Season 12 finale, Andrew actually brought her back to try and get through to Krystal before her final drive, showing that while Krystal might not have taken much on board from the experience, Mariah certainly did.
Daniela from Season 12 managing to pass the trailer challenge despite struggling during the lesson. How? She took the initiative and used Google to research ways to help.
Tyler, the one who asked for the lessons, managed to pass on his first attempt.
Another Tyler moment from Season 12 was his near perfect run on the Mega Challenge. He passed through every part cleanly (the only hit he made was on a rim in the precision driving) and was given a round of applause from the experts and Andrew. (As well as one of Andrew's shirts, which he had asked for.)
Andrew finally hitting his limit in the Season 12 finale, giving up on the final drive with Krystal and finding his own way back (thanks to the camera car). Not only that but deciding Krystal didn't even deserve the CWD trophy and instead, giving it to Tyler as a reward for being the final graduate.
Jillian (Canada's Worst Driver 11) returning as a nominator for Ashley (Season 13). Not only is she much calmer this time around, but she's able to support Ashley the best way she can.