This Ableton tutorial walks through the curve-shaping tools inside the MPE Control device, using a setup where aftertouch is mapped to loop length in Sampler. The device displays incoming MPE data visually, and a dial to the left of that display lets you reshape how the input values are translated before they reach your instrument.
Adjusting the curve shifts emphasis toward a specific range of the input, so light pressure or heavy pressure can have more or less effect depending on where you set the shape. You can also define minimum and maximum limits, either by typing values directly or by dragging the curve handles, and invert the curve entirely if you need the response to go the other way.
For more complex mappings, a third breakpoint can be added to the curve, making S-shapes and other non-linear responses possible. The two segments on either side of that breakpoint can be linked or unlinked, giving you fine control over how each half of the input range behaves.
The same curve tools apply to Slide and Pitch, accessible from a chooser in the top-left corner of the device. All three curves, Pressure, Slide, and Pitch, are adjusted independently, so you can dial in a different response shape for each dimension of expression without affecting the others.