The in-form Julia Goerges stormed to victory in the final of the WTA Elite Trophy as Coco Vandeweghe suffered a startling slump in Zhuhai.
Second seed Vandeweghe led 5-2 in the first set on Sunday, but was blown away thereafter as her opponent won 11 of the next 12 games to triumph 7-5 6-1.
Goerges, last month's Kremlin Cup champion, has now won successive titles on the WTA Tour and this ninth match win in a row is projected to lift her to a career-high ranking of 14th.
"I can't imagine a better ending to this season. Two titles in two weeks - and this is the biggest one," said the German.
Vandeweghe, who lost her cool as her error-count rose sharply, can at least take heart from the fact she will move into the world's top 10 for the first time on Monday.
There was no hint of what was to come as Vandeweghe won the first three games of the match.
She duly moved into a 5-2 lead, but Goerges quickly turned things around with two breaks of serve before a stunning cross-court winner wrapped up the opening set in style.
A clearly frustrated Vandeweghe was immediately broken at the start of the second and had lost seven games in succession by the time she finally halted Goerges' streak by holding serve to trail 1-2.
Any hopes the American had of fighting back were swiftly extinguished thereafter as Goerges reeled off the next four games to secure the biggest title of her career in emphatic fashion.