One synonym for "most deep sixed" is "completely buried." This expression refers to something that has been thoroughly hidden or entombed, much like a treasure buried in the ground. Another synonym is "utterly destroyed," which implies that something has been so thoroughly dismantled that there is no hope of repair or salvage. Similarly, "obliterated" conveys a sense of complete annihilation and eradication. "Erased" is another option, suggesting that something has been wiped clean and removed entirely. Finally, "expunged" connotes a legal connotation, indicating that something has been officially removed from records or documentation.