Some antonyms would be: Decline, cessation, or halting.
"Initial" and "final" are antonyms. "Initial" refers to something that occurs at the beginning or the start of a process, while "final" pertains to the end or conclusion of that process. Thus, they represent opposite points in a sequence or timeline.
http://thesaurus.reference.com/browse/process?qsrc=2890 has a list of synonyms and antonyms
Antonyms
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What are the antonyms for cavernous
what isbrief of antonyms
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yes antonyms are opposite
Antonyms for "die" include:live
antonyms for said