Rex Storming the Castle in "Rabble". He takes down about seven Evos, cures two of them, and never stops or breaks into a run.
And then just a few minutes later gets his butt handed to him in an MOA for Quarry.
The end of "The Forgotten" where Rex outsmarts White Knight by making him look like an even bigger ass and gives full credit to the Providence soldiers WK had verbally trashed moments before. Our hero! Perhaps that week of Training from Hell did Rex more good than it seemed at the time.
"What Lies Beneath"
Rex: What does it look like? I'm curing him.
Another stunning moment comes from Six after Rex breaks a vital piece of machinery Biowulf angrily comes at him and immediately Six is there with his swords at Biowulf's neck and tells him to not even breath or else. This troper did not see Biowulf take a breath.
Dr. Holiday got a particularly epic moment she got where she saved Agent Six and Rex by rapid-firing at a huge monster, driving it back. Six's gobsmacked expression said it all.
Not to mention that Rex destroyed his own contingency plan. The thing White Knight had specifically designed to take down Rex should it prove necessary was destroyed by him, while Rex was suffering from exhaustion and the Mini Mecha was at full capacity with its intended pilot. Serious Bad Ass points for Rex.
Six vs. White Knight. They both get multiple MOAs during that one fight.
"Payback" gives us new!Rex vs. new!Kleiss. It is suitably epic.
The whole episode is epic. In this episode there is also:
Dr. Holiday (and sibling) vs. Skalamander
Noah just grabbing a gun and joining the fight against all the Evos.
Six vs. Van Kleiss's Mooks and vs. Van Kleiss himself
White Knight giving Biowulf a piece of his mind.
Even the nameless Providence soldiers get one for blasting back Van Kleiss's invasion forces.
Don't forget Bobo Haha. When Rex and Noah are about to be beset by a bunch of Evos, Bobo shows up and blows them all to smithereens.
Bobo Haha: You see what you get? [throws away BFG] That's what happens you interrupt. My. NAP. Bobo gets cranky![starts blasting with dual pistols] Rex: I learned that the hard way, too.
Dos has a minor but fantastically delivered one in "Divide By Six":
Rex: (having just heard Dos speak some Spanish) ¿Eres de Mexico? Dos: ¡España! (smacks Rex in the face with his cane)
Rex and Six have a joint one later when they, in perfect, wordless unison, take down Dos, Tre, IV, and Five.
And then there's Six's retort when Dos question Rex's usefulness.
Dos: This boy cannot possibly save a man like-
Six: This boy has faced things that would make YOU people RUN AND HIDE.
Even more awesome when you remember that whatever Rex has faced, Six has as well. Once again, we are reminded that being only the sixth deadliest man on the planet does not in any way stop him from being the most Badass.
Rex's brother Caesar breaking into Providence to rescue his little brother.
The first thing Rex does in the very first episode is an MOA. He freefalls from a Providence ship at breakneck speeds, and punches a giant EVO so hard he ends up knocking him out in one shot. Bad. Ass.
And that's just how it starts! Among other highlights is Ben going Upgrade and merging with Rex. Sure, it's not what wins it, but dang was it awesome to watch!
"Black and White" gives us Black Knight vs. White Knight. Really, the whole episode is wall to wall awesome.
Also, Captain Calan is White Knight's inside man. To keep the pretext around Black Knight's people, he willingly and smilingly let White Knight punch him in the face. Gotta respect that.
"Deadzone" has Rex tear through an entire Providence squadron with ease. By the end, there's not a single vehicle in the air.
Holiday knocking Scarecrow out with a pipe at the end of Mind Games.
In "Assault on Abysus", Rex has teamed up with Biowulf to gain access to a Master Control Nanite, when Providence attacks. They tear their way through the EV Os, but when they cross Rex he leads them into a trap that takes them all out. Once these happens, all of the EV Os left standing begin chanting Rex's name. Made even sweeter by the fact that earlier Skalamander, a former enemy of Rex's, told the Providence agents that Rex was gonna kick their asses.
When Rex is being Shelled by the Black Pawns. Circe and Biowulf pull a Big Damn Heroes. Circe blows a few away while Biowulf swipes at their leader. HE gets knocked back, and looks fine, until Biowulf tosses up the Alpha nanite that they were looking for, having picked the Pawn's jacket with his long claws.
Also one for Providence's The Cavalry moment toward the end, where it's also revealed that the majority of Providence turned back to White Knight's side.
Rex turning into giant mech made up of his Omega-1 nanite builds and wrestling the Consortium.
Also, when Rex encounters Cesar again, he says nothing to him. All he does is walks up to his brother, punch him in the face hard enough that Cesar falls to the ground, and keeps walking. Stone cold. Stone cold and awesome.
Van Kleiss gets one for tricking everyone into thinking he really did go insane until he finally made his move to take the meta-nanites for himself. It didn't pan out but he still played everyone like a fiddle.
Last one goes to Rex again for using the meta-nanites to kick off a revolution by curing nearly every EVO in the world. The music that accompanies the scene also counts as a Crowning Music of Awesome.
And, of course, the series ended on a high-note with "Rock My World", the entirety of which Rex spent beating the hell out of legions of evo-clones in the form of the most obnoxious kind of ugly jerk, accompanied by an Animation Bump and great music.