n.an unexpected winner; someone who defeats the favorite competitor

Upsetter
Upsetter
ELECTRIC UPSETTER
Out goes Nestlé's upsetter
Automatic hydraulic cold-upsetter
The Spirit, an Upsetter, Turns Life on Its Head
Upsetter ratings.(ASK JIM)(James Henning answers to technical and operational questions)(Brief article)
Structural behaviour of pipeline upsetter design: a finite element study
Design and analysis of hydraulic system for 160kN electric upsetter
King Tubby meets the Upsetter at the grass roots of dub: Some thoughts on the early history and influence of dub reggae