Batman has saved the people of Gotham City more times than they can even count, but that does not mean that they have been spared from a far amount of tragedy also. Every time a villain wants to strike at the Batman, they do it through going after Gotham City, they go after his city.
The people of Gotham are resilient though and continue to endure all the horrible events that are thrown at them. Batman fights hard for his city, but it is when his city is being torn apart that he fights even harder.
10 Zero Year
Batman: Zero Year was written by Scott Snyder and drawn by Greg Capullo and was used as the new origin for Batman in the New 52 universe. It saw Batman in his fledging days as a crime fighter going up against the likes of the Riddler. In order to rule Gotham, the Riddler flooded the whole city and kept the citizens trapped, he then ruled from above, looking for anyone to challenge his intellect.
9 Swamp Thing Takeover
During Alan Moore's historic run on Swamp Thing we saw the protector of the Green takeover Gotham City easier than any one in the rogues gallery has ever done. He covered the city in foliage and trees and returned the concrete jungle back to nature. He evens takes down Batman during his brief attack on the city. Swamp Thing is incredibly powerful and can easily return the world to how it used to be if he so chose.
8 DCeased
In Tom Taylor's alternate reality version of the DCU, DCeased, the Earth has been overrun by people infected with the Anti-Life Equation, making them into zombies of sort. Gotham City is not free from this terror, and not even Batman and his family can hold them back. In the end Gotham was filled with zombies who ran amuck over the uninfected, and not even Batman himself was free from this plague.
7 Joker War
The Joker has had many nefarious schemes over the years, but the recent story arc Joker War saw one of his most destructive yet. He took Batman's fortune and used it to finance total anarchy in Gotham, giving his followers access to all of Batman's ordinance, the city became one huge never-ending riot. The very citizens who lived there were responsible for tearing it down.
6 Cataclysm
One of the most devastating things to happen to Gotham City is the earthquake that kicked off the story arc, Batman: Cataclysm.
One evening, a 7.6 earthquake struck the city, tearing it apart. Wayne Manor and the Batcave are destroyed, the city is in ruins, and the only buildings left standing are owned by Wayne Industries because they were made earthquake proof. The entire Bat-Family returns to Gotham in order to help rally the city.
5 Night Of The Monster Men
In one of the first crossovers on Rebirth, Tom King's Batman run kicked off Night of the Monster Men. This event saw Hugo Strange send a group of manufactured monsters to run rampant over the city. He made them to reflect the images of what he saw to be Batman's biggest flaws. They destroyed a large portion of the city until Batman and his team were finally able to stop him.
4 Endgame
When the Joker finds himself becoming bored with Batman, he decides that it is time for their game to end at last. During this attack by the Joker, he releases a deadly version of his toxin onto the streets of Gotham in massive doses. This version of the toxin causes people to turn their feelings of love and affection into incredibly vicious and violent outburst. The city is thrown into a violent chaos, with the people tearing each other apart.
3 City of Bane
Gotham is not a place for the faint of heart to live, with Batman's litany of villains, there is always another one planing his downfall. In Tom King's Batman run Bane played a big part throughout multiple story arcs that all culminated in City of Bane.
This story saw Bane take over Gotham city once and for all, he installed other villains as police and high ranking officials and he ruled the city and it's citizens with an iron fist. This of course lead to chaos and bloodshed in the city and havoc reigned until Batman could save them.
2 Contagion
Gotham City is more than just the brick and mortar of the buildings, it is the people, and it is for the people that Batman works so tirelessly. So when a strain of the Ebola virus is weaponized in Gotham, Batman is almost helpless. Batman: Contagion has Ebola being introduced into the city by the Order of St. Dumas. It ravages the population to the point that Gotham is put into a city wide quarantine in order to stop the spread of it to other cities. Although physically the city isn't destroyed, its population is badly hurt by the virus.
1 Death Metal
The most recent event, Dark Nights: Death Metal sees not only Gotham in ruins, but the whole DCU. It has all been reshaped and changed in order to fit the needs of The Batman Who Laughs. Gotham is part of the Hellscape and is ruled over by some of the worst versions of Batman. The city that once was there is demolished and in it's place is a new darker Gotham, one that can never be saved, unless the whole multiverse is saved.