There is none that are good by God's standard. There are none that cannot believe in fact all believe. They simply do not want to believe what they know to be true about God. Their desire is to create a god that suits their image of what and who God should be. They are all liars. They know it and God knows it.
For the cause of Christ
Roger
With that attitude, I doubt you will leave an impression on true skeptics. We need to understand their skepticism and address that instead of beating them over the head with the word. We need to humbly draw back sometimes and let God work out His plan for them.
Once we get into the mindset that God is not trying to save the world, right now, we will become more effective as witnesses. Sometimes we can witness against you, or your stance, and still witness to you. Catch my drift? Sometimes we need to just shake the dust from our feet and move on.