Anti A.T. Field
An Anti A.T. Field (アンチＡ.Ｔ.フィールド) is the term given to a type of energy that S² Engines are capable of producing which neutralizes existing A.T. Fields. The result is that individual A.T. Fields - the light of the soul, barrier of the heart, the "ego" - collapse, and the soul is freed from the body. In Lilim this results in the individual's body reverting back to its original form of LCL. This happens because a body cannot maintain its shape without an A.T. Field.
The Anti A.T. Field generated by Adam in Second Impact was powerful enough to exterminate all local life, including microorganisms. If Adam had not exploded, it's possible that the Anti A.T. Field being generated by her would have been able to exterminate all life on Earth. Instead, the entire South Pole was "formatted" into an uninhabitable "dead sea".
In The End of Evangelion, at the beginning of Third Impact, the Mass Production Evangelions use their combined S² Engines in conjunction with Evangelion Unit-01 to create a large Anti A.T. Field which destroys much of the surrounding Tokyo-3 area, revealing Lilith's Egg in its wake.