Rear side glass goes up and down hard.Cure?

Pretty hard to troubleshoot without looking at the hardware, but when I've had that in the past, it was one of two things. Yours might be different.

If the fuzzy channel is worn, the window can jam at an angle. Sometimes it can be resolved with an adjustment, but it usually means replacing the channel. Raise the window as far up as possible, then back off the handle enough to remove the load. Grab the window on both sides and see if you can raise it a small amount that way, then repeat. If that's the case, it's probably the channel.

I have also had worn gears that jam, but more often it's ancient lubricant that has turned into a gummy, and sometimes almost dry material. A thorough cleaning to remove the old material and fresh lubricant can fix that problem unless the gears are shot.