Lighthammer is a common term for all energy weapons optimized to be used against planetary targets. Or, to exact, against planets - using medium calibre MAWs and vasers as a precise weaponry to disrupt planetary defence is something completely different than using Lighthammer-grade weapons to destroy the planet itself. Most of the Lighthammers are manmade grasers or rasers, with potent powersource allowing them to fire with enough power to instantly vaporize oceans, annihilate cities, level mountains and - with grasers - also add a lot of gamma radiation for added damage against any lifeform. If used for a longer while against a single point, it can even melt through the planet mantle. Beginning a lot of decidedly unhealthy processes. Using energy weapon in atmosphere means wasting a lot of energy, so it isn't a very popular type of worldkiller MDW, but it does happen from time to time. Especially since the extent of damage can be controlled and the planet might be sterilized but not completely levelled down.