The burly French heavyweight fell victim to a massive overhand right by Roy "Big Country" Nelson at 2:03 of the first round.
Despite a superhero-like physique and serious kickboxing skills, Kongo has never been able to put it together against upper-echelon opposition.
It's striking basics that a shorter fighter's most effective punch against taller opponents is the overhand, and Nelson made no attempts to disguise his intentions. From start to finish, Nelson remained crouched in a low stance measuring for the move.
Against top opponents, Kongo tends to shell up and become hesitant.
There are some serious deficiencies in Kongo's striking defense, but perhaps his issues are beyond minor technical adjustments.
At 37 years of age, Kongo's ability to sustain punishment is deteriorating. His body won't be able to withstand many more knockouts like the one he suffered on Saturday night, and it'll be interesting to see how he rebounds.
Here are five fights he should take next.