'Most bombed' as in:
When it comes to amount of raids, bomb tonnage etc, cities like Berlin, Hamburg, other large German industrial centers would quickly float to the top, as Germany has been subjected to (western) Allied air attack for years, ramping up especially from the mid war years. Berlin was attacked a lot, but also heavily defended for nearly all of the war. Hamburg suffered a very deadly firebombing raid in '43, amongst other regular attacks, Hamburg being an important German industrial center and port city after all.
Regarding outright destruction and human cost, one cannot ignore some of the cities in Japan. Even though Japanese cities were not subjected to bombing campaigns for as long as mainland Germany was, Japan was at this point, late in the war, much less able to defend against bomber attacks than Germany was for most of the war.
The bombing of Tokyo in march '45 (9-10 march) with firebombs created a firestorm of incredible proportions. Modern casualty estimates are well north of 100.000 people, which makes it the single most destructive bombing raid in history. Vast swathes of the city were destroyed.
The atomic bombings as well were, of course, incredibly devastating regarding destruction and human casualties.