You present such an ignorant view Palivec
These lists don't care if a city was destroyed or not. Frankfurt was completely destroyed too, but is #7 on the Mercer list.
Try to compare the level of destruction of both cities to have a balanced opinion .
Bombing of Frankfurt am Main by the Allies of World War II killed about 5,500 residents and destroyed the largest specify medieval city center in Germany.
en.wikipedia.org/wiki/Bombing_of_Frankfurt_am_Main_in_World_War_II
Now the facts about Warsaw :In December 1939 the first mass shootings of civilians takes place in the Kampinos Forest near Warsaw where by 1943 thousands would be killed. In 1940 round-ups (lapanki) of civilians on streets and in homes became the norm. Those who did not manage to escape were sent to death camps at Auschwitz and Majdanek or forced into slave labour in Germany
After the remaining population had been expelled, the Germans begun the destruction of the remnants of the city. Special groups of German engineers were dispatched throughout the city in order to burn and demolish the remaining buildings. According to German plans, after the war Warsaw was to be turned into nothing more but a military transit station. The destruction of the city was so severe that in order to rebuild much of Warsaw a detailed landscape of the city, painted by the Italian artists Marcello Bacciarelli and Bernardo Bellotto, which had been commissioned by the government before the Partitions of Poland had to be used as a model to recreate most of the buildings.
en.wikipedia.org/wiki/Planned_destruction_of_Warsaw
The population of Warsaw by the end of 1944 - 0
Our extraordinary capital city of Warsaw and its people who lost their lives fighting for her will live forever .
pl.wikipedia.org/w/index.php?title=Plik:Warszawa-panorama_z_fabryki_rteci.jpg&filetimestamp=20091227134358