Definitely a tough call, but I'm going to say it's a toss-up between Mikage's duel and Ruka's duel.

I've been thinking about it, but I really can't choose...  I'd end up with a list at least 10 duels long.  I'd probably start with... Wakaba's, then Juri's (last duel, then first), Revolution, all of Touga's...  See?

hayaba wrote:

Wakaba's duel was probably the most emotionally intense for me, because it was just so sad to see her so corrupted, and I really could relate with her reasons for dueling. Every time I listen to the theme from that episode I get a bit emotional emot-gonk

Yep, Wakaba's rage and anguish does it for me too. Makes the duel *snap*. Add to this Utena's loyalty to her friend and refusal to fight (therefore greatly increasing the danger!) and it goes *snap snap*. Add to this Anthy's actually almost angry looks toward Utena as she orders her to draw her sword (after all Anthy's gone to a LOT of trouble to set this one up! She actually wore something different in her hair for once! ) and it goes *snap snap snap*. And the ending where only Wakaba's tear falls into "hell"...she's saved by Utena...powerful stuff...

jelli wrote:

At the end of his duel, he realizes how horribly pointless it all really was. The picture frame cracking and then falling, the moment of silence...I think it was definitely the most heartbreaking of all the duels.

This Mikage moment was huge for me too. It's an incredible duel because he's sorta going insane during it, babbling wild stuff about Tokiko and Mamiya, and in the end he loses everything, even though he didn't have anything. Amazing energy.

lex

I'm going to go with a lot of people and say Juri's first duel. When I watched it, it was intense and the fact that Juri is highly skilled and could have easily beaten Utena is a great tension builder.

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Loved this duel too - how fun it was to watch Utena really on the ropes. And who doesn't love the ending with the "miracle", and the shocked Juri/Utena looks, and Anthy's lovely spiteful little "have an orange rose dahling" gesture.

Ok I also add to my own list the duel with Saionji and the "disappearing sword of Dios". Firstly I love it when Saionji duels because he always looks so flippin' insane. Honestly, he has a great "crazy face". There's such a lot of tension in this duel...first-off Anthy is just standing there while swordless Utena gets whacked around (probably thinking about what she had for breakfast). And then slowly, suddenly, she finds her heart for a moment and remembers their conversation about helping friends from the night before. And so she *leaps* in front of Saionji, and draws Utena's soul-sword for the first time. A turning point for Anthy's character. (Check out the meaningful gazing between Anthy and Utena at the duel's close)

Who wasn't blown away they first time they saw the "pulling sword from rose bride's chest scene" reversed...now it's the prince who leans backward, and both together call for revolution. Akio (busy banging Touga) seems pretty happy at this turn of events, but really this is the moment in the game when he should be a tad worried. Wow, what a duel.

And finally for me: Akio's duel. Hoo boy, Akio actually sweating. Looking worried. Not smirking. The castle starts crumbling...the astounding power of this duel for me is the idea that Utena is winning. That she might ultimately win! You can see this idea in the dismay on Akio's face and his fumbling, and the shock on Anthy's. And of course, the way that Akio/Anthy win the duel is one of the most powerful moments in the series.