The single greatest sin people can commit is idolatry. God devotes a major portion of the Ten Commandments to this issue. He understands that the single greatest decision we must make is to determine who God is and what He is like.
Adam and Eve wanted to believe that they were the gods of their universe. But God quickly convinced them otherwise. Throughout history, people have sought to accept the true God, but then fashion Him into a more “acceptable” suitable image. This, too, is idolatry. In our effort to “adjust” God to someone who was less demanding, or righteous, or exclusive, we sought to take charge and to put God into a subservient role. Yet God refuses to yield His sovereignty to us, just because we have delusions of divinity.
The single most important realization we can have is that God is God, and there is no other. Once we understand this, we must share this truth with as many others as we possibly can.