Qualify for a Double Encore

Complete a bass event

Pull over while the police are in 'pull over' mode, then drive away during the ticketing cutscene.

String up one henchman and drop him to surprise a second (any play mode).

Spirit of Amadeus Arkham revealed

Glide continuously for over 100m

Complete story mode on Easy difficulty

Ride Titan henchman and knock down 10 thugs (any play mode)

Venture into Killer Croc's lair and come out alive

Solve 55% of riddler challenges

Complete a combo of 20 moves (any play mode)

Capture and lock up Harley Quinn