Weidman beat the GOAT at the time on arguably the best streak in UFC history, defended 3x. That is high, as far as highest highs go.
To getting a starring role in everyone's highlight film, having his face permanently changed by Yoel and his leg snapped like a twig. And it was all very public, unlike guys like Moraes, Barao, Pulver, etc who fell off the radar relatively speaking.
BJ was WW champ and LW champ, top 3 p4p, had a horrendous and never ending decline, but it wasn't a freefall drop fall from grace, he had the draw with Fitch in a title eliminator and won the Hughes trilogy after his title run ended and before the losing streak. Not quite steep enough a fall imo.
Rockhold has accumulated arguably the best lowlights reel ever. If he was a multi time defending champ or top P4P, he would have a case, but his highs aren't high enough imo.
Chuck got old. That's forgivable. And he went out on his shield, or as he would say, "got caught." He died a warriors death, or 5 warriors deaths. He is in the running.