Just making a single important orbit permanently uninhabitable can be pretty devastating.
Imagine a small satellite in a retrograde orbit close to the geosynchronous ring. The satellite is just a big hunting rifle cartridge full of buckshot with a tiny remote controlled gas canister that can turn it into a slowly expanding cloud of ruin. It will destroy everything in that orbit within twelve hours, hitting satellites at a relative speed of 6000 m/s.
[shudder] I didn't know I was that evil.