If the Vengeance is a doomsday weapon, then every single episode of ST has doomsday weapons. All the titular starships, and the Defiant, and a random warbird or Klingon warship, have the capability to lay waste to entire planets.

"The Vengeance was specifically designed to be a combat vessel and was larger, faster, and more heavily armed (with more advanced weaponry than other Federation ships of the same time period). According to Khan, Vengeance had "twice the size... three times the speed", and its warp drive was much more advanced in comparison to other Starfleet ships due to the Dreadnought class having been built as a battle cruiser. The Vengeance had been built to allow for a minimal crew and was largely automated. It was designed to be controlled by a single person if necessary. Its advanced phasers could be fired while the ship was at warp. The ship was also equipped with additional technologically-advanced features, including better shielding, more advanced transporters, and enhanced warp capabilities. The weapons systems of the Vengeance included an array of advanced phasers and two massive swivel-mounted torpedo launchers that could be deployed from beneath the saucer section. Vengeance could also launch drones which were, in turn, capable of launching several photon torpedoes before reaching and deliberately ramming their respective target(s). The Vengeance's phaser armament was extremely powerful – a focused barrage could penetrate the defensive shields of a standard starship (even at warp velocities), breach the hull and damage critical systems, and thereby force the other ship from warp back into normal space".
The Vengeance was also not used in a doomsday scenario, it was used to disable another (lesser) warship.
I'd say Admiral Marcus (and/or Khan's) plan of starting a full scale war between the Federation and the Klingon Empire for no reason sounds like a doomsday scenario to me.
As for the torpedoes: they didn't even have warheads. More like a long-range transport, used with motives that still elude me.
As I found out, not even fans of the movie know if the torpedoes were armed or not. Or armed but missing their fuel cells.
https://www.trekbbs.com/threads/paramount-going-ahead-with-st4-according-to-engage.285202/page-12
https://www.trekbbs.com/threads/paramount-going-ahead-with-st4-according-to-engage.285202/page-13
The plot of that movie was a mess.
Agreed!
