Thanks for the help guys!
I'm not even use it was in a The Flash comic, it might have been on another comic, like they used to have a main story (let's say, Batman) and then, at the end, there was a shorter story with another super-hero. But this may be just the way comics where printed in my country, it might be different in the originals.
I'm sure it was modern age, but I really can't remember which Flash it was.
The city that was flooded was not just a city, but it was important for The Flash character, so it could be Central City or Keystone City.
The villain used a big machine to create the tsunami by creating earthquakes in the bottom of the ocean. In the issue, Flash also used his phasing abilities to escape being buried alive by an earthquake.
I can try to translate particular catch-phrases he used, but they might be different from the originals as well. I remember he said "I could create a war by giving a headache to a major, or kill the president with a phone call."
The main reason I though he was Major Disaster was because he said that he had the power to control weather, but he exchanged it for the power to control probability (probably due to the same demon contract that says his powers don't work on himself).
The villain wasn't after the Flash just for fun, he seemed like he had been hired to kill the flash. At one point, while the Flash is trying to put sand on the beach to stop the tsunami, he uses a kind of binocular to blind the pilot of a news helicopters that was covering the story. The pilot shakes the helicopter and the journalist inside drops something that crashes inside the cabin of a truck, releasing the brakes and making the truck go downhill straight to the place were The Flash was. At this time, he said something about someone (probably the one who paid him to kill the Flash): "He hates you with the intensity of the sun."
Dunno if I can remember anything else =/