What's the cruellest defeat you've seen in motorsport?

Senna loses the 1989 Japanese Grand-Prix to Alain Prost and Jean Marie Balestre

Brazil 2008

There is only 1 the most cruell. Massa losing his title.

https://youtu.be/mlJWwuV9eBw

The 1998 battle for the WRC when Sainz’s Corolla broke down

Damon Hill at the 1997 Hungarian Grand Prix

At a local classic-car “race”, some years ago.
A Golf 1 GTI and a Fiat 500 (the original) Abarth (not exactly sports cars, I know) side-by-side.
Left turn, the Fiat “slides” along some haycubes, and that slows him down enough for the Golf to win by, like, 20 centimeters.

Carlos Sainz loosing the 1998 WRC championship only 400 meters before the finish line.

https://www.youtube.com/watch?v=liBLqmeHht8

Well, it was in 2016, on the Touristenfahrten laps at Nürburgring. Just as a young man with his russian friend topped the 10 minute mark, the poor little mazda basically beld out. Bitter defeat.

The first thing came on my mind

This is just heartbreaking to watch. https://www.youtube.com/watch?v=0OdW-VXgMl4