I'll let a Greek philosopher (probably not actually Epicurus, though usually attributed to him) make the connection.
Is God willing to prevent evil, but not able?One of the most common solutions to the problem of evil is to say God has "mysterious ways" and these acts serve some greater purpose. But God is supposed to be omnipotent. Not just really, really powerful - all-powerful. If he were all-powerful, he could achieve the same purposes without the killing and destruction.
Then he is not omnipotent.
Is he able, but not willing?
Then he is malevolent.
Is he both able and willing?
Then whence cometh evil?
Is he neither able nor willing?
Then why call him God?
Some people say that God can't be morally judged the same as humans, but I don't see why not. Whether something is moral or not isn't determined by the actor's power or knowledge. (Note to self: write a post going into more detail about this.)
One of the most... interesting... solutions to this problem that I've seen is that natural disasters are caused by human evil and sinfulness and for God to prevent them would interfere with our freewill. Of course, there was no explanation of how humans cause natural disasters, or how God would be interfering with freewill by eliminating them.
And then of course, there is the solution that there is no such entity that is omnipotent, omniscient and omnibenevolent. Personally, I find that to be the most parsimonious solution.