It's hard coming up with original, compelling characters in video games. In the quest for larger rosters, some developers have used slight alterations and color swapping to make it seem like their titles had a multitude of unique fighters. The following are some examples of actual de-evolution in fighting games.
Dan is de-evolved from Ken and Ryu from Street Fighter II - Dan first appeared in Street Fighter Alpha, wearing a pink gi and hurling autographed pictures of himself. Clearly, he's a comical version of Ken and Ryu, only with weak special moves and a little fart-cloud Hadouken.
The Ninjas are de-evolved from Scorpion and Subzero from Mortal Kombat - By the time Ultimate Mortal Kombat III had become the obvious favorite among arcade rats across the country, the game had amassed an army of ninja characters (some instantly selectable, others unlockable), one for almost every color of the rainbow. Reptile, Noob Saibot, Ermac, Rain and Smoke all fought either for or against the Forces of Shao Kahn and they were all mere doubles of Scorpion and Sub-Zero, except with different color costumes. Flawless Mockery!
Christie Monteiro is de-evolved from Eddy Gordo from Tekken IV - Although I'm sure the fans appreciate the developers going the extra mile and giving the Eddy Gordo copycat, Christie Monteiro boobs and some new outfits, there's no denying that she fights and controls exactly like Tekken 3's capoeira master. Still, most people would rather watch her fight than Eddy.