The phrase "final onslaught" refers to a powerful and decisive attack or effort made at the end of a battle, war, or competition in order to achieve victory. Full definition
In a statment by his Special Assistant on Public Communications and New Media, Lere Olayinka, Fayose said: «Since last week Thursday that Buhari appeared for less than two hours at the Chatham House where he said his doctors certified him fit and that he was returning to Nigeria for the «final onslaught on the PDP,» he has simply disappeared from the public glare. (dailypost.ng)
Deep throat sources at the seat of government hinted this paper that the «new appointees», who are to lead President Mahama's final onslaught in office, will be released in November, adding that «the President has almost concluded on ministers and deputy ministers and chief executives to be reshuffled.» (ghanapoliticsonline.com)
Apparently the Fathers of the Church interpreted that which held back the final onslaught of the Gates of Hell as the conversion of the Roman Empire, and believed, most of them, that the Parousia, or Second Coming of Christ, would follow the final persecution, a persecution which would follow on from the fall of Christian Rome. (faith.org.uk)