Try and get 3 medals on Jokers Carnival challenge map. Now that is an abolute bastard. I have passed the 100 hit mark for combo's on this several times and getting nowhere near the 1000000 score required for 3 medals.
Try and get the freeflow perfection achievement - it's a bit of a bitch but doable!
Got the 50 hit combo cheevo last night. Popped as soon as I stopped thinking about getting it. Strangely enough I've noticed that it's much easier to lose the rythm in the fights once the main story was over. I'm getting hit right left and center and it feels as if the window for counters is much shorter now than during the main story. But it is still fun and I'm just past the halfway mark in terms of total completion.