I'm surprised nobody mentioned Salvador Sanchez. That's in many ways the closest example, IMO, because it happened the same way, at even younger age, and there was already tons of aura about him.
Boxing was huge in that era. Sanchez' death translated far beyond the sports world, especially in Spanish speaking countries. I remember it being the lead story for days on Spanish networks here in Miami. Everyone was stunned.
However, I thought Sanchez was a bit overrated. You couldn't say that at the time but 4 decades removed nobody is going to threaten to kill you. That would have been reality in certain circles in 1982.
Kiptum is the most numbing and tragic example because he was likely to reset the parameters in an event that was already becoming higher profile.
I do suspect there will be young Ethiopians and Kenyans who reach Kiptum level much sooner than some are projecting.
Let's see, Monica Seles is properly included. That has to be near the absolute top. The Japanese swimmer Rikako Ikee looked to be a forthcoming superstar until shockingly being diagnosed with leukemia about 5 years ago while still a teenager. She survived and still competes but is more a feel good story than Olympic medal contender. Never the same.
Many racehorses suffered tragic fate. During that gap of 25 years of no Triple Crown winner between Citation and Secretariat, a key variable was that several never made it to the starting gate, like General Duke in 1957 and Hoist the Flag in 1971.
