If

Proposition #1: Suffering proves God does not exist.
If the Proposition #1 is True: Then nothing matters. Nothing. Life has no purpose and meaning. Why be angry at someone that doesn't exist? The question is moot. Case close.

Proposition #2: God does exist, He is not all powerful.
If the Propostion#2 is True: Then God has His limits. There is no hope pain and suffering will ever be eliminated. If God can't, who can?

Proposition #3: God exists, but He is not good all the times.
If the Proposition #3 is true: Then this God, when He feels like it, can add to our pain and suffering. Life is unfair as it is, so we say. Who would want a sadistic and unpredictable God beside?

If we believe any or all of the preceding propositions are true, we are back to nowhere. We are better off on our own, God or no God.