What is it that triggers the crossing of the line between a religious belief and the Reality of truth?

I'm at a crossroads. God is said to be merciful and forgiving. But God also tortures unbelievers for an eternity with fires and all kinds of methods of torture that only the world's sickest sadists could possibly enjoy. God knows all, so God knows we were created to be tortured eternally. Somehow reconciling this with a God of good or mercy is difficult for me.