Here is the full list of all 19 The Hong Kong Massacre achievements.
First boss completed
25 Doors destroyed
Picked up 50 weapons
100 enemies killed
Completed a level without slowmotion
First level completed
First enemy killed
First weapon unlocked
Died 250 times
Second day completed
1000 enemies killed
One hour in slowmotion
Completed a level on first try
Complete first day without dying
10 000 enemies killed
Complete the first and second day without dying
All challenges completed
All weapons and upgrades unlocked
Game completed