Depends on what you define the worst loss to be.
If you define it as losing with the biggest on-paper talent discrepancy, it's MTSU 2022.
If you define it as losing a game in which you had the highest expected win percentage, it's GT 2023.
If you define it as losing a game in which you had the most to gain by winning it, it's Syracuse 2024.
If you define it as most frustrating loss with something on the line, maybe it is SMU. But that's probably recency bias. My vote would be Syracuse last year. As embarrassing at MTSU was/is, it's year 1 and we weren't winning anything that year. GT wasn't frustrating as much as it was horrifyingly embarrassing. We won the game somewhat convincingly, until we did the dumbest **** of all-time. But Syracuse, you're up 21-0 against an average team, with a playoff berth on the line. Hold on, you're in the playoffs. Blow it, you're not. It was totally cut and dry, black and white. And we blew it.