it is unlikely that it carries any weapons... cough... cough...
it is unlikely that it carries any weapons.
Depends what are you trying to hit.
An ion drive accelerated kinetic can be as small as you wish. The size of a cubesat. If you are not in a hurry to hit the target and the target is another satellite you can send it off on a nice long journey to slingshot around the moon and whack whatever you want with 10km/s. Bonus points for doing the orbital mechanics so that it hits the target head on adding its orbital velocity to its escape velocity.
The energy released by whacking something with 15kg at 18km/s collision velocity is roughly equivalent to a kiloton of TNT. No satellite will be able to maneuver out of the path, it will be too late by the time they see it.
20-30kg kinetic with terminal velocity around 40km/s gets you into atomic weapons range. For that you will need to send it on a rather long excursion but if you want let's say an asteroid incident above the North Korean launch facilities...