The last level is "difficult" in much the same way as winning the lottery is "difficult". It seems nearly random as to whether the 1/84 of a pixel you're standing on/will hit is the exact portion you need to be on.
I feel like when someone kills the God of Light, the other gods would take notice. When you kill a second god they'd get antsy. About the time you kill your third is when the strongest gods decide it's time to deal with this guy...and you get unwritten from existence.