Here is the full list of all 20 The Hong Kong Massacre trophies - there are 5 bronze, 6 silver, 8 gold and 1 platinum.
All trophies unlocked
Game completed on normal difficulty
All challenges completed on normal difficulty
All weapons and upgrades unlocked on normal difficulty
10 000 enemeis killed
One hour in slowmotion
250 deaths
1000 enemies killed
25 Doors destroyed
Second day completed
Complete the first and second day without dying on normal difficulty
Complete first day without dying on normal difficulty
First weapon unlocked
First Boss completed
Picked up 50 weapons
100 enemies killed
Completed a level without slowmotion
Completed a level on first try
First level completed
First enemy killed