A Roman execution device isn't exactly a picturesque scene of divine love on display. It'd be the equivalent to having three criminals side-by-side in electric chairs. Or a firing squad having their criminals in a line with crowds watching and laughing. We'd never turn that scene into jewelry or bumper stickers; it's disturbing. The cross is a symbol of torture and cruelty, blood and death. It highlights the abuse of power and an undeserving punishment. Yet it's in that place that God does the scandalous. He turns the excruciating event of the cross into the perfect display of a scandalous, unmerited love for the undeserving.
In 2 Corinthians 5:21 Paul writes, "For our sake he made him to be sin who knew no sin, so that in him we might become the righteousness of God." The scandal of the cross is that in a moment Jesus becomes the worst of the worst and we put on the righteousness of God.
On the cross, Jesus becomes the worst sinner of all time. In a moment, there is no sinner worse than what Jesus becomes on the cross. The sins of all people in all times and in all places get put onto Jesus.