Didn't think about other sports which are technically allowed by the question. If we're going to go down that route then you can't argue against Cael Sanderson who went 159-0 in 4 years.
You did not specify which sport, so I'm going to go with Lew Alcinder. His UCLA teams won 3 straight titles (freshmen didn't play back then) and were 88-2. One loss was to Houston when he had an injured eye, and the other was to USC, who played stall ball all game since there was no shot clock.
Others that come to mind are the wrestlers who went undefeated throughout their college careers. Dan Gable might have done that, and possibly another guy more recently, but I don't feel like looking it up right now.
When they change the rules because of you, you know you're a bad mofo.
Gable did not go undefeated - lost only one match, the NCAA championship as a senior.
The one you're thinking of recently was Cael Sanderson - 159-0, four NCAA titles. Jesse Owens would probably the dominant athlete in a single sport (four world records in a hour?), but Sanderson would go as 1-B.
For multiple sports, hard to argue with Jackie Robinson - lettered in four sports at UCLA - All-American running back in football, led the Pac-10 basketball conference in scoring twice, won the NCAA long jump title. I'm told he also played baseball.
•9 NCAA Titles
•14 All-American Awards
•23 Big Ten Championships
•Honda-Broderick Cup Award - top US female collegiate athlete, '90
•3 Big Ten Athlete of the Year Awards - now called the "Suzy Favor Hamilton Award"
•Big Ten Athlete of the Decade for the '90s
•World University Games Silver Medalist
•NCAA Woman of the Year
•Babe Zaharias Award
•Big Ten Network "Icon" - Picked by the network as the #19 ranked athlete and #1 female athlete in the history of the Big 10 Conference
This. On the mens's side, it's tough to say,but, I'll put a vote in for Jesse Owens