Beware the Nice Ones/Professional Wrestling


 * Often used for a Face Heel Turn; for example, when Bob Backlund made his early '90s return to WWE, he was portrayed as a nice older guy who loved to compete and served as a mentor to the younger wrestlers on the roster -- right up until he snapped, putting Bret Hart in the crossface chicken-wing out of jealousy, and becoming an uber-reactionary psychopath. WWE owner Vince McMahon's evolution from goofy good-guy announcer to maniacally lecherous and evilly manipulative corporate boss following the Montreal Screwjob (see Dropped a Bridge on Him) is another good example, also an example of Real Life Writes the Plot.
 * Though sometimes the face doesn't turn heel, they just reveal that they've Took a Level In Badass. The Undertaker is particularly adept at this.
 * John Cena can typically be counted on to be a guy who's pretty calm and relaxed and willing to joke around and playfully mock his opponents, and when competing in fair fights will still find plenty of time to have fun. Piss him off a little too much, though, and he'll start doing things like throwing around 500-pound men, ripping pipes out of the machinery and taking them to someone's face, and trying to run people down with forklifts.
 * And that's just physical harm. When he's given a Hannibal Lecture by The Miz and R-Truth, what does he do? Nothing except turn it against them into a "The Reason You Suck" Speech that's so powerful, it made them fight one another.
 * Kofi Kingston is a pretty level-headed guy who is often seen with a smile, but if you push him over the edge, he'll hit back hard. On the 10/26/2009 edition of WWE Raw, after losing the WWE Championship in an Iron Man match to John Cena the previous night at Bragging Nights, a livid Randy Orton ambushed Kofi, claiming he was the reason he lost, with Kofi clearing Orton's Legacy teammates out of the ring, after getting blamed by them for costing team Raw the 7-on-7 tag team match. A little later, Orton's Legacy teammates tried to calm him down with a custom Nascar car. Soon after that, while Legacy was in the ring, Kofi broadcasted himself on the titantron as he defaced Orton's car, his face alternating from mischievous glee to uncharacteristic anger. It got worse in the following weeks.
 * And exactly what happened in his most recent fights with Ted DiBiase.
 * And Dolph Ziggler. Does no one learn from history?
 * Jimmy Jacobs. My God, Jimmy Jacobs. Who would have thought the same person who wore furry boots and played a giant for laughs would turn out to be a complete psychopath who would hang a bleeding Jay Briscoe from the ceiling and shower in his blood?
 * Melina Perez (fits it more as a Face than when she's heel) walks down the ramp smiling and waving to the fans but when the bell rings she is an aggressive screamer who goes to the limit.
 * For a good face example, look at Eve Torres. Sweet, happy girl who looks so much like Wonder Woman I'm surprised DC hasn't threatened a lawsuit. However, if you push her one inch too far, she will put her Brazilian Jiu Jitsu training to good use and will snap you into several little pieces. Check out her "The Reason You Suck" Speech to The Miz and her attempts to climb over Michael Cole's "Cole Mine" after he dumps on her matches a little too much. Similar things could be said of Natalya, Beth Phoenix, and Gail Kim.
 * Prior to his 1987 heel turn, Andre the Giant very much fit this trope, with many announcers referring to the big guy as a gentle giant. Whenever a heel crossed his path and used devious means to try to take him out, Andre became brutal and used his aggression to make the bad guys regret their moves. Famous examples came with Killer Khan, who was thoroughly beaten in a legendary stretcher match (the objective being to injure the opponent so severely they need to be taken out on a stretecher) at the Philadelphia Spectrum; and Big John Studd and Ken Patera (after the two knocked Andre out and cut his hair).
 * As part of the Andre-Studd feud, Andre once appeared on the WWF's Tuesday Night Titans (a takeoff of The Tonight Show) to discuss his feud with Vince McMahon. When McMahon persisted with questioning about Andre putting his career on the line vs. Studd's $15,000 at the first WrestleMania, a clearly annoyed Andre (who did his best to keep his temper and smile) grabbed McMahon by the necktie and told him he would fight the WrestleMania match on his terms before walking off the set.