I haven't played COTG on a regular basis in about 20 years but I am starting to get back to that side, even as I continue to play the Legends side of things.
The one character change for storyline purposes that I remember loving the most was when I turned Massif heel. This would have been with his original card and probably taken place sometime in 2089 or 2090, game-wise. I just remember him turning on Commander Sam and Star Warrior vowing revenge for Massif going over to the heel side. Except, Star Warrior really didn't understand. Massif wasn't joining the heel side of the GWF; he hated Thantos equally as much as he now despised Commander Sam, Omega and Star Warrior.
No, Massif wasn't going to be a heel or a face. Massif was going to be looking out for Massif and what benefitted Massif from now on.
Massif took the Heavyweight Title from Thantos pretty handily, attempted to injure Thantos so that Massif wouldn't have to deal with him and then set his sights on taking the real trophies, as he saw it: the careers of men like Omega, Commander Sam, Kraken, Star Warrior and so on.
Massif went from being one of the GWF's most popular wrestlers to their most hated in a matter of weeks.
And I loved playing every minute of that out.
I also turned Massif heel pretty early on. Thantos originally used mindgames on Massif to make him turn on his FDF teammates, and then I had a bootleg faction leader called the Cultist team Massif up with Bishop Hell. Massif & Bishop Hell turned out to be the most dominant tag team in my fed's history, and Massif had a couple of runs as the Heavyweight Champion as well.