Here are four core arguments against God's existence that have persisted since ancient times. Using these four arguments as an organizing principle, I present for your consideration the Four Enlightenment Horsemen of 1737-1776. These years represent the time when all four were alive, but Voltaire was born in 1694 and Paine lived until 1809.
The argument from evil- If the gods are real, they have a lot of explaining to do. Voltaire saw god as a mythical tyrant.
The argument from inconsistent revelations- Sectarian religions are mutually contradictory and internally inconsistent. Benjamin Franklin found Christianity utterly incoherent.
The argument from reasonable nonbelief- If the existence of the gods were self-evident, everyone would believe. The burden of proof is on religion. As Thomas Paine observed, special pleading is not evidence.