The Planet Killer, living up to its name.

The new flagship of Abaddon the Despoiler, and also his new WMD, Planet Killer is a gigantic (Even by 40k measures - it is stated in-universe that ship of that size is impossible to build in real space) battleship built around its main weapon, the seven-barreled Armageddon Gun. It also has a flak ton of other firepower, mostly VERY powerful lances, lots of torps, etc. Best way to deal with it would be keeping away and spamming torps, which is how the Planet Killer was destroyed in the fluff. Didn't stop Failbaddon from reclaiming and rebuilding it.