Yuji Sakai upon seeing his friend Hirai about to vanish after just one day manages to get her to exist a bit longer by forcing the whole class (but especially Ike) to acknowledge her existence. She still fades away, but it convinces Shana to use her torch to take over her identity.
On that note, "Hirai" (as possessed by Shana) becomes a holy terror for all the teachers of the school, telling the first teacher to study the subject properly. Perhaps this is why in the second season, everyone seems to spend most of their time goofing off rather than studying.
The typical MacGuffin-carryingOrdinary High-School StudentNon-Action Guy, who has been something of a Distressed Dude for most of the show and slowly developing his powers, finally gets some respect from the fans when he kills off Zarovee's five selves one by one, actually breaking one's neck with his bare hands. Granted, Yuji's power was explicitly stated to dwarf Zarovee's (who had been relying on a hostage situation), but nonetheless, he crushed a guy's throat in with his bare hands.
Then in Season 3, he makes an entire army retreat in tears with a speech.
Really, a big part of the series is about Yuji taking a level in badass. By the end of the first story arc (the Friagne arc), he had gone from Ordinary High-School Student who had traumatically learned the truth about himself and the world to somebody whose insights and advice proved instrumental in defeating Friagne. In the Aizen sibling story arc, he worked with Margery to identify and destroy the siblings' power sources. In the Dantalion arc, he first used [[BFS Blutsauger]] in battle. By the second season, the pace of his training, at the hands of both Shana and Wilhelmina, has accelerated, and he becomes powerful enough to handle minor threats like Zarovee and even land a hit on Shana while sparring (and it is noted that his potential is equal to that of a Crimson Lord). By the end of this season, he has begun to fight alongside Shana in actual combat. By the beginning of the third season, he has merged with the Snake of the Festival to become a Physical God and leader of Bal Masqué, capable of matching Shana in combat. He cripples the Flame Haze Army, and out gambits Shana and her little band of Flame Haze during the final battle for the fate of Xanadu. He gets his own unique spell, Grammatica, which is capable of doing pretty much anything, which he retains even after he and the Snake of the Festival split.
Wilhelmina is hinted at being fairly strong, but you don't realize her true power until episodes 20 and 21 of season 2, where she battles the implacable assassin Sabrac, dealing blow after awesome blow even after being struck with gradually opening wounds. The battle includes faking Sabrac out with a fake Yuji, setting her bandages to explode like magical remote mines multiple times, and crushing Sabrac between two buildings and then nuking them. The fact that Sabrac, The Destructive Blade, take all of this abuse without even flinching (and with amusing self-criticism) makes it a Crowning Moment Of Awesome for him as well.
The entire cast gets one in season 2 episode 21 when they finally take down Sabrac, complete with an utterly awesome Theme Music Power-Up.
Episode 13 in the first season give us two Crowning Moments Of Awesome, Shana's My Name Is Inigo Montoya and Margery Daw's Big Damn Heroes scene, both of them the turning point in their respective battles.
Khamsin and Rebecca's rampage in the Seireiden.
Tenmoku Ikko fighting his way to Shana, taking out Fecor (and cutting through Magnesia!) in the process.
Wilhelmina, Rebecca, and Khamsin's fight with Sabrac. He proceeds to take them 3-on-1, Implacable Man-style, wounds Wilhelmina and Rebecca, and No Sells an attempt to beat him the same way as beforenote By removing his body from the ground and destroying it by binding the surroundings to his body.
That scene with Shana going into a rampage while attacking Snake of the Festival Yuji with her trademark Tsundere BAKA! qualifies as this is the first time in this season that she let go of her bottled feelings (since Episode 4) and her stoic facade that she's been wearing all the time.
The final battle between Yuji and Shana (with Sydonay and Margery Daw). Also counts as a Crowning Moment of Heartwarming and Crowning Moment of Funny (for when she just headbutts him from a fit of good ol' teenage drama). At this point both protagonists just throw everything they have at each other, including the spell that can become any spell, Grammatica, and massive bursts of crimson fire.
The climax of the movie — Friagne uses the Trigger Happy Treasure Tool to force Alastor out of his pendant. Needless to say, Alastor gives Friagne hell for almost killing Shana in the process.