It depends on you. 

1. Do you want the ending where you want to wake up from the nightmare? 
>! Don't fight the penultimate boss, and accept his offer.
2. Undeniably the worst ending. 
>! Don't accept the penultimate boss's offer when you don't have three Umbilical Cords.
3. Do you want to see the nightmare to the very end? 
>! Don't accept the penultimate boss's offer when you have three Umbilical Cords. 

Personally I think the first ending is the best.