Another 1 that qualifies would be Tyson-Holyfield 2. After the huge shock in the 1st fight people were expecting another thrilling HW fight in the sequel to see if Tyson can avenge his loss, not to mentioned the fight did 1.99 million PPV buys, the most ever at the time (now surpassed by Oscar-Floyd). The fight ended with a huge thud when Tyson bit Holyfield's ear robbing fans of a worthy sequel.

So I would say imo this is the most disappointing fight in history because of what happened. This was at the sport's premier division, not to mentioned the most bought PPV at the time.