Great question. Had to think long and hard about this because every win and loss matters haha.
The best way I can answer is to say before the Saban era, wins were "bigger" and losses were "smaller." This means my sweetest victory was probably the '92 natty, with the two victories over Spurrier in '99 battling each other for second and third sweetest. I attended the victory in the Swamp and was surrounded by Gator family members, which makes that one particularly "sweet" for me! Now when Grimes ran that interception back for a TD in the conference title game, I literally ran out of my apartment door yelling at the top of my lungs disturbing everyone in the community. Probably the most unhinged I've ever been haha.
The most sour loss, Jesus, like others have said, Kick Six (missed opportunity for a three-peat), first loss to Clemson on final play, second loss to Clemson (inexplicable blowout) with our amazing 2018 roster, the loss to UGA in the natty after taking the lead in the 4th, loss to Michigan in Saban's final season (I'm sorry we beat DeBoer in the natty if we get past Michigan, and Saban retires on top!) ... I guess I'll go with the blowout loss to Clemson because that was the only time we looked unprepared for a huge game. It's the worst because it's the most confusing.
***Honorable mention for sweetest win: that come-from-behind victory late in the game against Arkansas in Saban's first season, after years of collapsing in the 4th QT under Shula. Everyone forgets how much that victory inspired Bama Nation.
***Honorable mention for worst loss: that OT loss to Tenn in the Shula era when all we had to do was keep them from converting a 4th and 20-something! That was devastating at a time when we went what 7 seasons without beating them, maybe 8 including the tie in '93, which I was also at.