Natwest (NWG) had the highest return between 2003 and 2007 by a US stock with a market cap of $50B+, returning 9,034,940%.

ASSET	YEARS	% RETURN
Natwest (NWG)	2003-2007	9,034,940%
National Grid PLC ADR (NGG)	2003-2007	1,704,843.75%
Monster Beverage (MNST)	2003-2007	8,307.29%
Cheniere Energy (LNG)	2003-2007	4,921.47%
Axon Enterprise (AXON)	2003-2007	4,163.7%
Apple (AAPL)	2003-2007	2,658.07%
Intuitive Surgical (ISRG)	2003-2007	2,526.15%
Williams Companies (WMB)	2003-2007	2,493.2%
Southern Copper (SCCO)	2003-2007	2,025.47%
Petroleo Brasileiro Petrobras SA ADR (PBR)	2003-2007	1,997.51%
Petróleo Brasileiro SA - Petrobras (PBR.A)	2003-2007	1,944.96%
CME (CME)	2003-2007	1,530.06%
America Movil SAB de CV ADR (AMX)	2003-2007	1,273.93%
Itau Unibanco Banco (ITUB)	2003-2007	1,161.26%
Booking (BKNG)	2003-2007	1,081.69%
ICICI Bank (IBN)	2003-2007	940.93%
Canadian Natural Resources (CNQ)	2003-2007	928.37%
HDFC Bank Limited ADR (HDB)	2003-2007	908.17%
Cummins (CMI)	2003-2007	889.44%
Trip Group Ltd ADR (TCOM)	2003-2007	870.68%
NVIDIA (NVDA)	2003-2007	750.38%
Valero Energy (VLO)	2003-2007	660.58%
Freeport-McMoran Copper & Gold (FCX)	2003-2007	651.74%
Quanta Services (PWR)	2003-2007	628.89%
Suncor Energy (SU)	2003-2007	616%