You may be correct in referring to the MOUND CITY incident as being the most destructive in terms of loss of human life aboard a Naval vessel in battle, and, although there were a couple of other losses through natural disasters, I believe the BAINBRIDGE was the most destructive in that context.
Incidentally, amongst other losses through battle, how many crew were killed in the COMMODORE JONES and SHAWSHEEN, in May, 1864, or aboard the TECUMSEH, when she was hit by a torpedo, August 5, 1864? I think the TECUMSEH may be pretty close, if not more than the MOUND CITY.