Natwest (NWG) had the highest return between 2003 and 2008 by a large-cap US stock, returning 1,589,066.7%.

ASSET	YEARS	% RETURN
Natwest (NWG)	2003-2008	1,589,066.67%
National Grid PLC ADR (NGG)	2003-2008	1,082,643.75%
Monster Beverage (MNST)	2003-2008	6,264.92%
Deckers Outdoor (DECK)	2003-2008	2,312.83%
Axon Enterprise (AXON)	2003-2008	1,464.44%
Illumina (ILMN)	2003-2008	1,427.82%
Banco Bradesco SA ADR (BBD)	2003-2008	1,214.42%
Bancolombia SA ADR (CIB)	2003-2008	1,194.77%
ArcelorMittal SA ADR (MT)	2003-2008	1,182.9%
Apple (AAPL)	2003-2008	1,088.4%
Sociedad Quimica y Minera de Chile SA ADR B (SQM)	2003-2008	1,036%
Chunghwa Telecom (CHT)	2003-2008	996.6%
Williams Companies (WMB)	2003-2008	968.05%
Southern Copper (SCCO)	2003-2008	951.11%
Intuitive Surgical (ISRG)	2003-2008	932.49%
Petroleo Brasileiro Petrobras SA ADR (PBR)	2003-2008	829.44%
Petróleo Brasileiro SA - Petrobras (PBR.A)	2003-2008	810.95%
Alamos Gold (AGI)	2003-2008	774.3%
Vale SA ADR (VALE)	2003-2008	744.79%
Akamai Technologies (AKAM)	2003-2008	738.33%
Stifel Financial (SF)	2003-2008	726.12%
U-Haul (UHAL)	2003-2008	676.74%
Elbit Systems (ESLT)	2003-2008	663.3%
Booking (BKNG)	2003-2008	657.71%
NetEase (NTES)	2003-2008	654.81%

Large-cap stocks are treated as having a market cap of $10B+.