All jokers fault probably

Clock King (at least BTAS clock king, the one in the picture) can't control time. He just plans things very precisely and likes clocks. He's actually pretty cool in the one episode he's in.

That, and he has an absolutely giant monster clock.
- I heard that mf has like, 30 gdamn clocks
Clock King (at least BTAS clock king, the one in the picture) can't control time.

He did have access to a device in his second appearance that allowed him to control the flow of time, so he had the ability albeit in an indirect fashion.
- I came to add this.
This, I have only seen him in the show and yeah I don't remember him controlling time
He also shows up in JLU for the task force x ep
- Great show, and a great use of this character.

Canonically? Yes! A giant bat demon named Barbatos that creates twisted versions of Batman (including batman) to torture Bruce Q Wayne

There's also Dr. Gotham, who was a evil sorcerer buried under Gotham for centuries whos evil also apparently poisoned a fair bit of the area.

There's also anywhere between 1 to 3 (Possibly more) Lazarus pits under Gotham, and arguably the chemicals from them have been leeching into the water supply. What do the Lazarus pit chemicals do? Make you resilient to damage and also crazy. What do a significant amount of Bat villains have in common? Injuries/mutations that would kill a normal person, and being off kilter.

Then we have the Asylum which is possibly haunted and has held a portal to Hell at least at one point.

Lots of stuff going on in Gotham.
- I am here to doubt the validity of Dr. Gotham's degree and licensure.
- Your excellent summary has me imagining the day to day work of the staff at the Association for Gotham Tourism.
  
  That's gotta be weird.

Condiment King put all kinds of stuff in the water

Is lead a condiment?
- The Romans used lead as a sweetener...

Probably a Lazarus Pit or two

The problem is wealth inequality which the Waynes directly contribute to.

Good old redditor take that never read a comic book
- He's the biggest charitable donator in Gotham right? Directly runs all kinds of homeless shelters and shit?
- This is explicitly how things are explained in Harley Quinn. The irony of it is that it's Joker who points all this out.
- Good old redditor take that doesn't explain anything in a snide way.

I bet it's whatever chemical that's in those vats at Ace Chemicals that the upstanding citizens of Gotham kept falling into and come out as clowns.

Like, why would any company make a chemical which the only purpose seems to be to get psychiatrists to beat people up with baseball bats on roller skates?

Whatever is in the water probably seeped out of some Wayne Enterprises industrial plant. Batman is the biggest menace to Gotham City; not any of the victims that become villains. All because some rich playboy wants to play ninja instead of running the corporate empire that owns like 90% of the city.