Difficult

Joust

Play very passively, just try to defend military challenges. Also try to get a fair amount of influence on the table (but subtle, your opponent might notice and counter by brutally destroying it all). Then, when you see the time is there, play 'naming the heir' (plot card). Then, you must use an effect to reval a new plot card during the challenge phase (citadel law is ideal). This will let you bring 'summoning season' (plot card) on the table. Search your deck for 'Areo Hotah', raise your claim value to the level you need and suck every last bit of power out of your opponent with a power challenge (an effect that lets you initiate one more allways helps a lot). This might not give you an instant victory, but with 13-0 power it's not much of a fight anymore.

Requirements for the trick:
- Areo Hotah cannot be in play yet. (Subtility is gold)
- At least one effect that let's you change plot card during challenges
- A way of losing three challenges without your opponent suspecting a thing
- 8-10 power on your opponent's house card in the beginning of the round (which will increase to 12 by undefended challenges etc.)
- A brutal fighting force in the power category OR a way of crippling your opponent so that he can't defend (properly / at all) during this challenge
- ... (Maybe I didn't see that one thing, but don't stumble over it)

BONUS:
-Littlefinger in shadows
-The red Viper with a lot of gold
-Some gold to trigger effects (if you're able to predict the future, playing 'planning ahead' makes a lot of thematical and tactical sense)
-Archmaester Marwyn, ready to be sacrificed
-Event cancellation (but real heaps of it - you don't want the enemy messing things up right)

Killers of this strategy:
- An infamy deck
- A brotherhood deck
- A deck that can make an insane amount of power out of a couple of fortunate challenges (looking at you, Greyjoy)

(Warning: Reading this strategy will probably take longer then winning / losing the game)