Regulus Gale winning the tournament was awesome enough, but he goes against all expectations by not only defeating both Peter and Yikzhekel, two duelists who up until then had been utterly Curbstomping their opponents, but also manages to win despite both being Curbstomped at the beggining of the match, and the fact that he had the Lswarm virus poisoning him from the inside out. That kid deserves his victory.
Daniel Clemens becoming the first duellist to take down one of the cultists. With Red Nova Dragon no less.
The entire duel against the Constellar cultist is filled with these moments:
Peter playing possum in order to lure the cultist into a false sense of security and springing a sudden Mirror Force on her to suddenly turn the tables.
Caramon getting his second wind and managing to use Meklord Army of Skiel to finally take down the cultist after spending almost the entire duel as The Load.
The Cultist herself gets one for being able to completely dominate both duellists despite being outnumbered. She even manages to take out Swords of Revealing Light the very instant that it's played. When you can manage to stop them from even attempting a Hope Spot, you know you're a formidable duellist.
On a larger scale, its somewhat poetic that the two duellists to avenge Jacques are his best friend, and the one responsible for his most significant moment of Character Development.
The defeat of all three of Apophis' decks, ending with Art electrocuting and then spearing the Big Bad with a rush of attacks. Then Apophis True Form is defeated by Marduk by the use of Exodia pieces, and with a little unexpected help, the first Big Bad is put away.
Sigmund. In breaking free from Apophis' horror world. He was the only one to see it for what it was right from the outset. Add to that the exact way in which he broke free: By helping the woman to break free, and that beginning to show the cracks.
Marcus' curbstomp of Denero's father. One turn, over 8k lifepoint damage after what seemed like complete incompetence from Marcus.
In the earlier parts of the story, Marcus' deconstruction of Gretel, sending her into a near mental and emotional breakdown. This was both horrifying to see, but also an omen of what this boy could do when pushed.
Amidst the battle with Denero's parents, Marcus goes off on a speech aimed not only at Haine and Denero's parents in an attempt at deconstructing their psyche, but one aimed at exposing all that he is as well...That and his use of "Adorable" and "Cute" when talking about Haine managed to piss said kid of to no end! Marcus was the only one able to send Haine off the edge into wanting to watch him suffer unimaginable pain. Bad. Move.
Peter. What can one say, but that boy is a human Weapon! Throw on top if that his ability to take on the role of the shield as well, there is not much one can do against a dueling style applied in such a way.
In Peter's Grand Finale, he stood and met the end with a calm grace and dignity befitting one far beyond what many would consider mortal. Spending much of his time protecting his friends and allies from harm, leaving himself open to attack, he stood as the proverbial rock to which one clings through the rushing waters and the storm raging around.
During the Apophis worlds sequence, Peter was entombed within the very earth itself, felt his entire body rot and decay to the point where nothing remained, and felt the earth compress upon him, every insect within the earth crawling through him and still did not go insane!
Sylvestre. That poor kid. He chose to fight in a battle that (at the time) did not concern him, acquitted himself well for as long as he lasted, and managed to make us all groan in pain and secretly wish for his death for his god-awful puns!!
Haine. This little boy is Pure. Unadulterated. Evil. During his battle with Marcus and Sylvestre, and their subsequent torture, he activated and used the radios of the duelists to broadcast his torture of the two boys. All that can be said is: That was brilliant you evil little bastard!
Apophis. In just Its first move, It nearly called down two Worm Zero's AND Evil Dragon Ananta almost right from the get-go. Ouch! There is no way that one can overstate the sheer sense of impending doom from that one move.
Not only during the duel did It show such ruthlessness and single minded drive. Even before It breached our world It began a path of pure psychological warfare with just a single goal in mind. From the use of Haine as a tool, to the creation of separate worlds for the duelists, right up until the moment of the battle and Its fusion of the Duel Spirits as an avatar of sorts, using them as a shield so as to continue the fight at full strength after the duel was done. All this, just to destroy reality!
In the final duel, Apophis ordered Malefic Cyber End Dragon to literally TEAR PETER APART!! The dragon then proceeded to EAT the pieces of Peter until nothing was left. This was not only horrific, but it shows Apophis viewed Peter, our lovable, annoying rock to be his greatest threat on the field due to his ability to shield the others from harm. This was very much a demonstration of Apophis' pragmatic and single minded thinking to get the task done.
Freed. Nearing the final sequence, Freed brought Sigmund into his memory and challenged him to a duel. During this duel, he brought up many things that he wished Sigmund to learn from the mistakes he himself made in that time so long ago, seeking that one chance to atone for the sins he himself committed against his closest allies.
Gol'gar. This Duel Spirit made a valiant attempt at defending the one he considers as close to a brother as he will ever willingly concede to anyone. Within the Shadow realm Gol'gar attempted to directly strike at Haine whilst Marcus and Haine were dueling. Haine turned Gol'gar's strike back on him and proved that even by the Spirits, he could not be harmed so easily.