Atmospheric Deprivation Weapon

Atmospheric Deprivation Weapons, often called by their acronym ADWs and also known under the project name Light of God or Project 456, are a type of weapons of mass destruction developed by tbe Bureau of Experimental Military Research for the Terran Federal Navy in the early 27th century. They are currently considered to be the most powerful weapons available in the galaxy, and their development is strictly prohibited. Other than the Terran Federation which initially developed the technology, no other nation has ADW capabilities. The Convention on Weapons in Galactic Warfare in 2655 banned their usage. 
ADWs function by causing the temperature of a planet's atmosphere to rise to extreme levels, causing atmospheric ignition. Ignition is achieved following a lengthy process involving the liberation of flammable gases in the atmosphere. After a certain critical quantity is reached, the atmosphere is ignited with nuclear weapons. The sustained reaction of the atmosphere is sufficient to destroy the planet, though several tests have managed to reach atmospheric fusion. This is most effective on planets with large quantities of liquid water, which liberate massive amounts of hydrogen. The atmosphere's temperature rising eventually leads to a glow emanating from most Earth-like atmospheres, resulting in the appellation Lights of God.
Following the usage of the weapons, the bodies of water on the planet evaporate liberating massive quantities of steam in the atmosphere. This increase in greenhouse gas emissions means that the planet's surface will have drastically higher temperatures even after the artificial chemicals have returned to the ground. 
The project was first proposed by Bureau of Experimental Military Research engineers in 2598. Research continued throughout the 2600s but eventually halted in 2612 due to a lack of funding. In 2629 the project was transferred to Clarktech. Development accelerated significantly and by 2640 the preliminary testing had been complete. In 2642 the first real scale test, codenamed Ouranoboros, was completed in a system belonging to the Somne Combine. After approval by the Department of Military Development production was launched on a Clarktech-C2I jointly-run station named Installation H76x-CCT. 
The technology was unknown to the galactic and Terran public until Operation Tenbatsu, when it was deployed on three separate occasions. The most infamous of these was the Destruction of Kfaray between December 5th and December 7th 2644. The Ur-Han colony was rendered uninhabitable, and its population of 800 million was entirely destroyed by the process. In total, ADWs were responsible for the deaths of over a billion people. This makes them the deadliest weapons in history by far, having killed more people in three uses than all other weapons combined throughout the course of all of galactic history.