If none of the other guides are working for you, give this one a shot!
It is important to note that this is another luck
based achievement so it will require trial and error with a lot of patience while dealing with the randomly spawning skull!
After trying several different methods for over 2-3 hrs with no luck, I managed to get the IWHBYD skull after 3 attempts
by using this method:https://www.youtube.com/watch?t=1s&v=NKUgg_1Chjc
*YouTube video credit to xOGx RockStaRs
A few things to note:
1) The chance of the skull appearing is 1 in 7 so if it doesn't appear after the checkpoint in the room where the skull should
appear, restart the level, do not
2) Grenade jumping makes things easier but it is not necessary if you aren't comfortable doing it as all the jumps can be done while crouch jumping,
3) I did not have any skulls activated for my playthroughs,
4) I did not do a 360 degree spin like he did at the 1:04 mark and lastly,
5) I did not kill any enemies during my successful run.