I've been playing the combat challenge maps in Arkham City after I just wanted to play a simple combat game. And it's very satisfying. There's almost a zen-like quality to it when you really get in the flow and get those crazy long combos, effortlessly chaining different attacks and dodging enemies like Neo in the Matrix.
One map in the DLC however I feel is close to plain unfair, and that's the Joker's carnival one. It's basically a time attack survival mode where you have to keep a combo up so you can fill up a meter, and afer certain thresholds you can empty the meter for extra points and time.
The frustrating thing about it is that the medal thresholds for it are 100k, 500k and 1 million points, and if you get your combo broken even like twice you can kiss the two higher medals goodbye. A single hit completely resets the meter. Building it back up takes so much time, and you only start with 3 minutes, that a single mistake, a single input error, can completely ruin your attempt. If you don't get a good combo going in the first 30 seconds or so it's basically not worth it and you might as well restart. I haven't even gotten to 500k yet, it feels just impossible. The combat system in that game is one of the tightest ever designed, but even it has cracks, and if even a single one of those appears (which it will), your attempt is ruined. I feel that if getting hit didn't reset the meter, but only knocked it down a level or two might make it more balanced.