Who finally sacked Rome and which emperor did he depose

Answer: While c. 476 CE is the traditionally accepted date for the end of the Western Roman Empire, that entity did continue on under the rule of Odoacer (r. 476-493 CE) who, officially anyway, was simply ruling in place of the deposed emperor Julius Nepos (who had been deposed by the general Orestes who had placed his son, Romulus Augustulus, on the throne).