Spin modifier Decelerate?

Roygee

OK - yeah, see what you mean:)

Did some messing around, using the spin modifier set at angles, with the timeline at 24fps.

Started at frame zero, with spin set at zero cycles per second, then set to three cycles per second at two seconds and again to zero at four seconds, using Bezier tweeners. Changed the sign at one frame after the three-second mark to a minus to try and fool it. It reverses the direction of the spin for twelve frames, then reverts to the original direction. Takes 24 frames to get back to the position it was in at the two-second mark.

So, if you render up to the two-second mark, make a new render from the three-second mark and combine, you should get a nice deceleration to zero:)