#8 Sgt. Slaughter
To an extent, this one could be labeled as the most shocking heel turn of all time, but it doesn't take the top spot on this list due to how controversial it was to the point that it was borderline offensive.
Vince McMahon was behind everything here, and although he had initial trouble with anti-American promos associated with this gimmick, the Sgt. loved it to. The August 1990 invasion of Kuwait by Ba'athist Iraq triggered a political crisis that would lead to the 1991 Gulf War, in which Kuwait was freed by a US-led military coalition.
A female WWE star said her life is in danger. Details HERE
The decision was made to have Slaughter support the Iraqi cause, not for the actual political reasons, but more for the fact that Slaughter liked "brutality" and the Iraqi government was "brutal" while Sgt. felt the US regime had become soft. He joined up with General Adnan and regularly trashed the US, with at one point revealing a (fake) photograph of he and Saddam Hussein.
This all leg to Sgt. becoming WWE Champion to lead to an Iraq vs. America match at WrestleMania with Sgt. defending with Hulk Hogan. Sgt. turned face after the angle.