this is a simple tutorial for a falling damage, using distances, because with the method of counting the time when you falling, can be affected by the frame rate of the game, with this method, the fall distances calculation will not affect by the frame rate.
first we need to create 3 global variables.
1- iY or initial Y, this is the player y postion when you start to falling.
2- eY or end Y, this is the player y position when touch the floor.
I am using the platform templete of C2.
now we create 2 events.
player--Platform On fall===== set iY to player.Y
player--Platform On landed===== Set EY to player.Y
subevent--system max_distance<or=int(distance(0,IY,0,EY))=====do the damage event.