The worst was not Dresden. The worst non-nuclear bombing attack was Tokyo which had a death toll 4-times larger than Dresden:
https://en.wikipedia.org/wiki/Bombing_of_Tokyo
In any event, historical context is important. 1945 was the worst year of the war in terms of human death toll.
The Nazi holocaust was marching relentlessly onwards, killing an average of 14,000 people per day. Auschwitz was only liberated 2 weeks earlier than Dresden but the Nazi death machine was still in full operation in points further west.
The Soviets were losing about 20,000 people per day on the eastern front.
Germany was losing about 10,000 soldiers per day during 1945
China was experiencing enormous losses (15 million deaths during the course of the war)
The USSR had nearly 6 million soldiers taken prisoner of which less than 20% survived the war
Germany held nearly 100,000 American prisoners of war
The war was a relentless death machine and every day it could be shortened would result in tens of thousands of lives saved. Did the bombing of German cities bring the war to a quicker end? Yes, undoubtably. It brought the German industrial war machine too its knees. Take away aerial bombing of German cities and how many extra months would the war have lasted and how many more people would have died? Who knows.
Was Dresden uniquely different from other German and Japanese cities that were bombed during WW2? From what I have read, no, not really. What made it unusual was the firestorm that resulted. Which was something that involved no small amount of luck (or perhaps chance) in that atmospheric conditions had to be just so. On a different day with different atmospheric conditions, Dresden might have been a more ordinary (and forgotten) bombing raid no different from dozens of others.
One can make a similar argument about many strategic military choices that involved civilians. Sherman's march to the sea, for example. Did that shorten the Civil War? I don't know but many have made that argument.