Here is the full list of all 48 Batman: Arkham Asylum trophies - there are 28 bronze, 18 silver, 1 gold and 1 platinum.
Platinum Trophy
Perform a perfect combo including all of Batman's combat moves (any play mode)
100% Complete
Achieve 24 medals on combat challenges
Achieve 16 medals on combat challenges
Complete a combo of 40 moves (any play mode)
String up one henchman and drop him to surprise a second (any play mode).
Achieve 24 medals on predator challenges
Achieve 8 medals on combat challenges
Achieve 16 medals on predator challenges
Defeat Titan henchman without using Batarangs (any play mode)
Complete one predator challenge by using only Silent Takedowns
Achieve 8 medals on predator challenges
Spirit of Amadeus Arkham revealed
Solve every riddle on the island
Complete one combat challenge without taking damage
Solve 85% of riddler challenges
Solve 70% of riddler challenges
Complete story mode on Hard difficulty
Complete story mode on Normal difficulty
Complete story mode on Easy difficulty
KO all the henchmen celebrating your arrival at the party
Defeat the giant Titan Ivy plant
Complete a combo of 20 moves (any play mode)
Ride Titan henchman and knock down 10 thugs (any play mode)
Venture into Killer Croc's lair and come out alive
Conquer the effects of the Scarecrow's fear gas
Catch a Batarang (any play mode)
Defeat two Titan Henchmen at once
Solve 55% of riddler challenges
Capture and lock up Harley Quinn
Solve 40% of riddler challenges
Save Dr. Young from being killed by Victor Zsasz
Face your biggest fears and keep your sanity
Gain access to Administration after it is locked down by the Joker
Glide continuously for over 100m
Solve 25% of riddler challenges
Defeat Bane
Survive the nightmare of the Scarecrow's fear gas
Save all the doctors in medical
Solve 10% of riddler challenges
Escape from Intensive Treatment to the island surface
Solve 5% of riddler challenges
Complete a combo of 10 moves (any play mode)
Survive the onslaught from the deformed Joker henchman
Rescue the guards and henchman from the Joker toxin in Decontamination
Take down Zsasz in the Patient Pacification Chamber
Complete a combo of 5 moves (any play mode)