The one ship no other can best (except one of it's own class)
Any Banks' Culture GSV-ships. Such as Unfortunate Conflict Of Evidence or Death and Gravity.
GSVs (General System Vehicles) represents the full spectrum of the Culture's capabilities, since it can access all of the information known by the Culture and can make anything that the Culture can make. Systems Vehicles are enormously magnified von Neumann probes, as their essential components are engines, multi-purpose factories and Minds (advanced artificial intelligences). With these capabilities a Systems Vehicle can function as anything its Mind(s) and the Culture choose.
General Systems Vehicles (GSVs) are the Culture's largest type of ship, ranging between 25 km and 200 km in each dimension (including the fields protecting them and forming the exterior of their life-support system). GSVs which provide accommodation for biological members of the Culture generally have populations in the millions or even billions, and can be considered worlds in their own right. However, they are also, with some lead time, able to transform into massive factories or warships. In one of the Culture novels (Excession), a GSV unloads its organic population and transforms itself into a very fast-moving shipyard/mothership, effectively deciding the outcome of the main plot thread.
GSVs generally have little resemblance to traditional 'ship' design expectations, as they are enveloped in multitudes of fields which allow them to dispense with anything resembling an outer protective hull or shell, instead often being covered with parks and outside buildings.
The Culture (and other societies) have developed powerful anti-gravity abilities, closely related to their ability to manipulate forces themselves.
In this ability they can create action-at-a-distance ? including forces capable of pushing, pulling, cutting, and even fine manipulation, and forcefields for protection, visual display or plain destructive ability. Such applications still retain restrictions on range and power: while forcefields of many cubic kilometres are possible (and in fact, Orbitals are held together by forcefields), in "Use of Weapons", a Culture warship uses its electromagnetic effectors to hack into a computer light years away.
In Excession one of the largest ships of the Culture redesigns itself to be mostly engine and reaches a speed of 233,000 times lightspeed.
The Culture also uses various forms of energy manipulation as weapons, with 'Gridfire' ? a method of creating a dimensional rift to the energy grid of Space-TIme, releasing astronomical amounts of energy into a region of non-hyperspace ? being described as a sort of ultimate weapon more destructive than condensed antimatter bombardment. One character in Consider Phlebas refers to gridfire as "the weaponry of the end of the universe".
Show me a ship capable of defeating the ultimate product of a post-scarcity socialistic utopia that spans entire galaxy. In only one book is the defeat of a GSV recorded: the ship took on the full half of the warfleet of an interstellar empire. And won, albeit extremely heavily damaged. Everyone assumed it gone, but the Lasting Damage from the book Look To Windward actually managed to return...