The Annihilator Cannon is a tremendously powerful type of Cannon found almost exclusively on Warships

So far, it is the most powerful kind of cannon available to ships in the entire world. 

Overall, it is made up of three smaller heavy artillery guns, with the main cannon located directly above. The sheer force and power required to fire the main gun is the reason for the three smaller ones. The triple guns, with their rapid fire capability, vent their excess heat into the main gun, which, when ready, fires a massive explosive ball which has been nicknamed the Juggernaut Round. This cannonball causes extreme damage, both from force of impact as well as the huge explosion that follows.

Given their size and weight, a warship can usually only carry one, two with heavy modifications made. The Hundred Thunder, the flagship of the Haven Navy, is infamous across the seas for having three.