Genome Skew Modifier
The 3ds Max Skew Modifier shifts vertices proportionally to their position relative to one of the bounding box gizmo's axes. The Genome implementation can bring the modifier even further by replacing the Limit Effect option with a Curve control for advanced skew effects not possible with the 3ds Max version.
The left image shows two undeformed boxes. The right image shows the native Skew modifier (green box) and the Genome modifier (blue box):
Once the Curve control is enabled and a custom curve is defined, the Genome Skew modifier can adjust the skew amount accordingly: