I've sketched out a a de-orbit mission for a satellite or wounded satellite at risk to enact a Kessler Syndrome.
Hitting with a conventional explosion threatens to fragment it. EMPs, Nuclear bombs and shrapnel are obviously no good at LEO. Using gas pressure is best. I suggest to intercept a wounded satellite, an unmanned rocket of compressed oxygen, or hydrogen, or helium gas be sent from Earth, to an orbit maybe a few kilometers above the wounded satellite and it gradually descends until it is ahead of the satellite. The rocket will need to cease firing its primary engine. It will have matched the velocity of the satellite. It turns around 180 degrees so its nose faces the satellite. It opens up its nose. The compressed gas is vented, immediately exerting pressure on the satellite, causing it to drop to a lower orbit. Venting gas will cause the rocket to increase speed, so it must begin pitching up and down, diving below and above the satellite to maintain the match of the satellite's orbiting velocity. As this pitching becomes more pronounced, less and less of the gas will impact the satellite. Eventually the satellite pitches to an ocean. It will be hard to get above the satellite if there is already a bad Kessler Syndrome, without Lunar logistics. With more time this mission may be made to work given existing space infrastructure.