WWE SmackDown delivered a chaotic night from Arena CDMX in Mexico City, with championship matches, major betrayals, and a shocking conclusion as Sami Zayn defeated CM Punk to become the new Undisputed WWE Champion.

The September 11 episode opened with Randy Orton reflecting on his victory over Cody Rhodes at Sunday Night's Main Event before warning the eventual winner of the night's championship match that he was coming for World Championship No. 15.

Randy Orton Sends a Warning

Orton addressed his victory over Cody Rhodes, arguing that while Cody is a good man, father, husband and friend, he isn't a killer.

Orton, meanwhile, embraced his reputation as a legend killer and made it clear that he has no problem doing whatever is necessary to capture championship No. 15.

With CM Punk and Sami Zayn set to battle for the Undisputed WWE Championship, Orton delivered his final warning:

Whoever leaves Mexico City as champion should be looking over their shoulder for the RKO.

Rey Fenix Retains the AAA Cruiserweight Championship

Rey Fenix successfully defended the AAA Cruiserweight Championship against Ricky Saints in an athletic contest filled with high-flying offense.

Saints came close after a powerbomb and Revolution DDT, but Fenix survived and eventually connected with the Mexican Muscle Buster to score the victory.

Winner and STILL AAA Cruiserweight Champion: Rey Fenix

Saints initially refused Fenix's handshake, although the two would later appear to make peace backstage, only for Saints to attack Fenix from behind and drive him into a garage door.

Nikki Bella Defeats Paige

Nikki Bella picked up a controversial victory over Paige.

Paige controlled much of the early action, but Bella managed to exploit an opportunity when she pulled Paige down and used the ropes for leverage during the pin.

The referee failed to see the illegal maneuver.

Winner: Nikki Bella

Trick Williams and Baron Corbin Continue Their Feud

Trick Williams celebrated Mexico's football culture and compared himself to Mexican football star Quiñones before introducing Lil Yachty.

Instead, Baron Corbin appeared and dragged Yachty toward the ring.

Trick chased Corbin backstage, only for Corbin to ambush him with a kendo stick.

The rivalry clearly isn't finished.

Chelsea Green Retains the WWE Women's Championship

Chelsea Green successfully defended the WWE Women's Championship against Nia Jax.

The match took another turn when Lash Legend attempted to interfere on Jax's behalf. Tiffany Stratton pulled Green out of harm's way, resulting in Legend accidentally striking Stratton.

Green took advantage of the chaos and hit Unpretty Her to score the victory.

Winner and STILL WWE Women's Champion: Chelsea Green

War Raiders Retain, Damian Priest Betrays R-Truth

The War Raiders successfully defended the AAA World Tag Team Championships against Damian Priest and R-Truth.

After the champions hit Truth with a powerbomb, Erik secured the pinfall.

The biggest story came afterward.

Priest initially embraced Truth and even placed a sombrero on his head before suddenly turning on his longtime partner. Priest dropped Truth with a clothesline and followed with South of Heaven.

A shocking betrayal.

Gunther and Finn Balor Escalate Their Rivalry

Backstage, Gunther told Finn Balor that his best days were behind him and suggested Balor should have retired years ago.

Balor responded by calling Gunther a "whiny little bitch" before striking him.

The confrontation adds another layer to the growing tension surrounding the Money in the Bank picture.

CM Punk vs. Sami Zayn Ends in Chaos

The main event saw CM Punk defend the Undisputed WWE Championship against Sami Zayn.

Punk appeared to be in control early, but the match quickly became a battle of attrition. Both competitors suffered injuries, with Punk favoring his knee and Zayn dealing with an injured wrist.

Zayn repeatedly targeted Punk's leg and came within inches of victory after hitting the Blue Thunder Bomb.

Punk eventually hit the GTS, but his injured knee prevented him from immediately capitalizing.

Then everything broke down.

Johnny Gargano and Candice LeRae appeared at ringside. Gargano distracted Punk, while LeRae interfered with the referee.

Punk trapped Zayn in the Anaconda Vice, and Zayn tapped out, but the referee couldn't see it.

Gargano then attempted to use the championship as a weapon, but Punk countered with the GTS.

Kevin Owens entered next and grabbed the title. He attempted to strike Zayn but accidentally hit Punk instead.

Zayn then delivered a low blow to Owens, hit Punk with the Helluva Kick, and scored the three-count.

Winner and NEW Undisputed WWE Champion: Sami Zayn

Sami Zayn Finally Reaches the Top

SmackDown ended with Zayn celebrating his first Undisputed WWE Championship victory while Punk lay stunned in the ring.

The championship picture is now wide open, with Randy Orton already declaring his intentions, Johnny Gargano and Kevin Owens embroiled in the chaos, and Sami Zayn suddenly sitting at the top of WWE.

Sami Zayn is the new Undisputed WWE Champion, and everyone is coming for him.