Another Crowning Moment of Awesome/Funny for Bohort: When Arthur gets fed up with Bohort's cowardice and ineptitude to fight, he decides to train him, beginning with hand-to-hand combat. After a full episode of Bohort failing to get even the basics, we see in the end that he finally manages to parry one of Arthur's punch, which in itself, is a CMoA. But then, Arthur do the same move, after telling Bohort to parry and counterattack. He reluctantly tries... And damn well knocks Arthur out.
Arthur, at the very end of Book VI — with the aspect ratio going from TV to cinema, and the caption Soon, Arthur will be a hero again.
The end of "L'Usurpateur", in Livre IV, is one of those: in the episode, Arthur was acting very strangely, doing things such as accepting an expensive (9500 gold pieces) request from Elias de Kelliwic'h without any thoughts or discussions, or being cruelly unfair with Merlin, telling him to clean and tidy the whole lab on his own. Then, you see the last scene: it was Elias, who was "shapeshifted" into Arthur for the whole episode. Why, you...
In Book V, Anna tries to convince Arthur to intercede with Léodagan for Loth and her. When he refuses, she has Loth zap him and puts a knife to his throat. Then Guenièvre bashes the both of them on the head with a huge shovel. Arthur can only stare.
Okay, this is a long one: "Lacrimosa", in Livre VI. Sallustius spent the whole season maneuvering in the shadows and designing a plan to get the Isle of Britain back under Rome's control: find a Briton (Arthur), get the "Sword of Kings" (Excalibur), and convince both the roman senators to name him "Dux Totius Britanniae" (Governor of Britain) and the Briton kings to accept him as the king reigning over the federated Briton kingdoms (with the help of the aforementioned Excalibur). Arthur, fed up of being a puppet, wants to get out of this without being the target of Sallustius or the Briton kings, which is made difficult when he learns that Sallustius is coming to Britain to sign the "act of property". His quickly-thought plan? He asks Mannilius to gather as many Britons as he can on the beach where they first arrived. Then, he goes to Sallustius, greets him, show him Excalibur, and explains that he did it: the Briton kingdoms and clans accepts the federation; he (Sallustius) only has to go to the beach and sign the treaty. He then goes to the beach before Sallustius, and trains the Britons on the spot with a rhetorical trick (= making them raise their hands when he says "soldier", and acclaim when he unsheathes Excalibur). Sallustius arrives, and Arthur calmly explains to him that Britons accept the federation and Arthur as a king, but they want the Romans out. Then, Arthur uses the tricks to demonstrate his point: "I'm Roman? Well I have Excalibur, look (unsheathes Excalibur, people sheers), "Yes, they're ready to fight, look." (go in front of the people, asks them who wants the Romans out by any means, finishing with "soldier"; cue everyone raising their hand) "I'm staying king here, and you become Rome's hero because you did what no other senator did: unite Britain back under Rome control. Now, beat it". The best part? Right after understanding he got screwed, Sallustius tries to go tell the crowd the truth: Arthur is Roman, and a bad one; his error? finishing on: "Honestly, who would want as a king a greenhorn who, not long ago, was only a mere soldier?" (cue everyone raising their hands)
The look on Sallustius' face when Arthur shows him Excalibur. This is when he starts to realize that his brilliant plan may be drifting away from his control.
In the very first episode of Livre VI (where, since it's that kind of season, every fan is expecting to see the protagonists during their youth), we learn that Manius Macrinus Firmus, the Dux totius britanniae (i.e. the Roman governor of Britain) has proposed a deal to the "Britain chief": a whopping amount of gold in exchange of a truce, with the knowledge that for a Briton chief, a treaty is like a sacred oath. When his aide-de-camp asks him if the chief might accept the gold and attack, Macrinus replies that you have to be smart to break an oath, while the chief is "thick as a plank". Then, at the very end of the episode:
Goustan: (sitting inside his tent, staring at a pile of gold ingots) Frankly, I feel embarassed. I, who thought the Romans respected their enemy... But no. Disillusioned yet again... If they think they're going to federate the country with that kind of mentality... I say we return their dough, we saddle up, and we smack in their faces! (beat) On the other hand, returning such an amount of money would be bordering on bad taste; sorry, but this isn't something to do, if only for the more needy. (smirks, then serious again) But then, there's the oath. If I keep the gold, I don't attack?... That's it, then. I keep the gold, I don't attack; an oath's sacred. (the camera, slowly traveling around Goustan, passes behind a silhouette; Goustan continues, to the silhouette) But what I find so upsetting is that this is the very day I'd chosen to hand over power to you. (laughs) Aren't dates something, eh? I keep the gold, I don't attack, I'm under oath. But you... (music rises) Now that you are King of Cameliard... If you feel like going and beating the shit out of them, I really don't see how I could stop you! (sticks his knife into the table, laughing maniacally; the silhouette heads towards the exit of the tent, and is revealed to be Goustan's son Léodagan while he speaks to his troops outside) Léodagan: Hey, guys! Guess what we're eating tonight? Romans! (troops cheering)