The simple answer to this of course is you do not "de-orbit anything large". In fact, such a thing is catastrophically wasteful since anything of significant m

The simple answer to this of course is you do not "de-orbit anything large". In fact, such a thing is catastrophically wasteful since anything of significant mass that has already paid the heavy kinetic energy toll required to get itself to orbit should be recycled for construction material. The economics work out very differently from the ground where normally the energy required to recycle something far exceeds that required to get a fresh supply. Anything too small for such use or too small to be directly targeted with ablating lasers (as another commentor suggested) can be de-orbited with normal light. It just takes a tiny amount of net momentum to send something on crash course for the atmosphere and since most debris lie on fairly well defined orbital bands, we can use reflectors to bath those swaths of space with enough light to gentle push anything there into oblivion. For anything that lies outside those bands, by the time we have enough infrastructure up there for those to have any significant chance of collision, we will likely have launch assist technologies like rotavators and orbital rings which means that station and vessels hulls can be made far thicker than the necessarily spartan standards of today.