Assuming you just want it to teleport the player to the nether roof where they are:
command /hell <player>:
trigger:
set {_x} to arg-1's x coordinate
set {_z} to arg-1's z coordinate
teleport arg-1 to location %{_x}%, 125, %{_z}% in world "whatever your nether world is called"
send title "Good Luck" to player
Keep in mind this is untested, if there is any errors feel free to reply with them and I can fix it up for you