9. King Mabel
While a lot of backstage heat seems to come from seemingly trivial incidents, 'very large man breaks big star's face with sloppy leg-drop' seems like a legitimately good reason for irritation. The sloppy leg-drop in question was delivered by none other than Mabel, or King Mabel at the time, and it led to a broken orbital bone for everyone's favourite zombie mortician.
The monster push that Mabel received in 1995 didn't look good at the time but it has aged particularly poorly. WWE was creatively circling the drain, Diesel's record-breaking WWF Championship run doing little for the company as Big Sexy lurched from one challenger to the next. For some unknown reason, Mabel was given the rub of winning the King of the Ring tournament and subsequently challenging for the title at SummerSlam.
A feud with 'Taker followed, a rivalry that began with the aforementioned botched leg-drop and broken orbital bone. There are few wrestling combinations worse than 'being absolutely massive' and 'being horrendously bad at wrestling', but Mabel was the perfect storm of the two. Injuring your colleagues is always a bad idea but injuring The Undertaker is insanity, and Mabel was soon out the door, supposedly at the behest of 'Taker.
The two would work together at various other points in the future, although the leg drops were few and far between.