Warsaw, Poland:
The nazis bombed the city with absolutely no regard for the civilian population in 1939. In 1944, after it was abundantly clear that Germany was going to lose the war, Hitler ordered the city razed to the ground. The Germans went house-by-house, street-by-street and block-by-block methodically leveling buildings - frequently those buildings were occupied, but the nazis handled that little problem by flinging grenades and incendiaries through basement windows where the civilians tried to take refuge. Survivors of this initial assault were rousted out of their shelters and shot in the street - men, women and children. It's estimated that between 150,000 - 200,000 civilians were killed in these mass executions. Artillery was called in, as were Stuka dive bombers. Germany received far less than it deserved.