So take a Falcon heavy, and run the middle core at low power, so you get it, along with the upper stage, which is basically an extra fuel tank with a docking adaptor, and get it to the ISS orbit. Then you do something not done since assembly, and start to move docking port, and attach the booster core there, and remove that module, moving the docking port into this now vacant position. Then the core stage does a deorbit burn, and aims to land semi softly at a point in the South Pacific, using the grid fins as long as they function to guide, and then using the reentry to burn all the parts up. Uses one per section, and the outer boosters return for reuse, dismantling the ISS over a period of a month or so, depending if they can keep the remaining parts of the ISS operating, though you can do a few dozen tons at a time.