What is your personal biggest "Whaf if?" from a UFC match?

For me personally, other than the counter uppercut which Tony Fergusson landed on Justin Gaethje in their fight, it has to be this moment right here.

I am sure nobody even remembers this moment, but I go crazy everytime I rewatch it. Khalil undercaught Pereiras kick perfectly and went for a Thai sweep but was just... JUST short. I always wonder what would happened if this sweep worked and sent Pereira flying like in some Muay Thai matches where some of the fighters damn near do a backflip mid air when their foot is kicked out from under them.