[Gunslingr3]

If he is omnipotent, nothing can happen against his will, or he is not actually omnipotent.
Which is more acceptable: that god can’t stop a 5 yo getting a raped, or won’t stop a 5 yo from getting raped?

[Varda]

Omnipotent means knows all and is all powerful. Knowing all and being all powerful doesn't mean being the reason for every action of those with free will.
God does not cause sin. Man chooses it.
If I drop a piece of steak on the floor, I know that my dog will eat it even before it happens but I did not make the decision or cause the dog to eat it.

As far as bad things that happen, there is more to them than we usually know. For instance, it's impossible for us to know how good something is without being deprived of it. Evil is the absence of the good.