This is just my opinion of course but I did some research and decided on a list of his 5 worst calls, feel free to let me know if I forgot any big ones.
5. Varner v.s McCullough - the mouthpiece controversy
4. Doerksen v.s Macdonald - indecision lead to excess damage
3. Burns v.s Johnson - eye poking fiasco
2. Velasquez v.s Rothwell - early/bad stoppage
1. Mir v.s Lesnar I - apparently didn't know what a tap out looks like