Disclaimer: I will not focus on Art or grammar, unless the latter would make the deck too difficult to understand.
Yeah, I can definitely see how Sun Yin is made to be a final boss. Let's get into it.
So, first things first, I actually like the deck overall? It really has all the "Final Boss" vibes going for it, and I enjoy that. The Power Moves in particular really struck me as fun and interesting, without being overcomplicated, and they do a good job of each actually building up tension without being too much on their own. Though I wonder if Spiritual Soldiers really warrants destroying the two at the end of the turn? The backstory of the character is actually quite interesting too: just "Nothing" for reasons why they are just as they are. Making sympathetic villains is fun and all, but sometimes you just really want someone you can punch in the face without a shred of guilt, and in that regard I like this fellow being the way he is.
I also need to give a shoutout to the Lash Out Against Losing of this guy hacking into your bank account to laugh at your balance. Like **** You too, mate xD
Now, for negatives... I'd say Hall of Heavenly Kings might need a clause of you not being allowed to use the second Plan to Win on the same turn it's played, or some other part of the inevitable chain might need slight brakes? A loop of Hall of Heavenly Kings -> Emperor's Generals -> Power Card move (with its Simple Card Move) I think might be too much even for endgame encounter opener, particularly with how much this deck can spam Respond Moves to make sure the player can't do anything. Pacing out the threats in the Finale is not a bad thing, I think?
I also have to say, I am not a fan of the last Plan to Win's thing of {Supreme} card Strength. There are plenty of ways to convey a card being nigh-invincible in direct combat or a trick encounter via effects. Atlas from the Book springs to mind as an excellent example with its negation of {Overwhelm}. And considering the sorts of things that have {Strong}+{Overwhelm} there, giving something explicitly made to be a step above just kind of strikes me off in ways I don't quite like?
Still, overall? Good job!