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