A term used to refer to a character, weapon, or entity that can wipe out a whole city. City busters are generally considered to be the type of characters that are not very strong but can solo low tier universes or some mid-tier verses.
In real life, citybusting can be accomplished with nuclear weapons. There are two basic types of nuclear weapons. The first are fission bombs which can produce a yields up to 500 kilotons of TNT. As the explosion of the bomb occurs, the fireball reaches millions of degrees Celcius at maximum and its volume rapidly expand. These are known colloquially as atomic bombs, A-bombs, or fission bombs. Fusion bombs are more powerful, and are known as thermonuclear or H-bombs. The largest nuclear bomb ever built was the Tsar Bomba, with a yield of 50 megatons of TNT (it was originally going to be 100, but they scaled it down). There is no theoretical limit to how powerful a nuclear weapon could be, however in practice they are not built so large due to scarcity of uranium/plutonium, the massive size it would require, and aftereffects consideration.
For OBD purposes, we can consider the absolute base of town/small city level to be destroying a small settlement of 1km in diameter (colloquially this would be considered a town), which would require about 5.3 Kilotons in yield. This leads up into cities with 10km diameters.
Mountain busting, and island busting has some overlap here, but is much stronger than the base of citybusting. The power it takes to excavate a crater is a lot greater than simply wiping the same area clean, but considering the size of the cities in the world, this is the reason for the overlap.
The next general level is "island busting".
Characters/Weapons that can destroy cities/create attacks equal to a nuke:
- A good number of Final Fantasy characters
- Top tier Zoids
- Any Toa from Bionicle can city bust with a nova blast
- Guyver Gigantic and several other beings from The Guyver
- Many Dragon Ball characters
- Most early Bastard!! characters
- Most of the Angels from Neon Genesis Evangelion
- Most Nanoha characters
- Silver Saints from Saint Seiya
- Starfighters and anti-starfighter weaponry in Star Wars alone
- Many Kaiju from the Godzilla series