Nuclear Option: The Imperial military is somewhat keener to use the Nuclear Option than most, partly because of the lack of a Nuclear Weapons Taboo, partly because nukes have a marvelous combination of characteristics that kill lots of things dead that conventional weapons are less useful against, like active bioweapons and nanoswarms, and also partly because when fighting on any number of hostile-environment worlds, you really don’t have to worry so much about mucking up the local ecosystem because no-one’s living in it anyway.

Also, it’s worth remembering that in the modern era, the Nuclear Option is generally carried out with antimatter bombs, which don’t leave hugely obnoxious amounts of fallout behind, and which can be calibrated downward to a nicety for much smaller explosions, compared to old-fashioned ‘splody-metal bombs.

Although for most purposes, orbital kinetic-kill strikes are almost as good.