I'm not sure the ISS has enough delta-v to get back down quickly. Lowering the orbit enough so that it will fall down in a few weeks is probably possible.
It's likely that a decent orbital dynamics model and a relatively small, well-timed delta-v would bring the ISS down within a rater small planned impact area. It wouldn't be necessary to decelerate very much to accomplish that. Remember that the ISS must periodically boost its orbit to compensate for frictional losses, on that basis it can be assumed that the craft's dynamics are well-understood:
