Well, there was this one time when...hey, what's with the psycho-logist.
The answer is Eclipse-class. It was the biggest Star Destroyer ever created and belonged to one of the clones of Emperor Palpatine. It had black paint, thousands upon thousands of turbo-lasers and ion cannons, and a superlaser at the tip of the SD. It was destroyed when Luke and Leia escaped from the Emperor's Force Storm that he had driven the ship into.
So the VSD (Victory-class Star Destroyer), ISD I and ISD II (Imperial-class I&II Star Destroyer), SSD (Super Star Destroyer), and ESD (Eclipse Star Destroyer).
New question.