Natwest (NWG) had the highest return between 2006 and 2008 by a large-cap US stock, returning 1,680,200%.

ASSET	YEARS	% RETURN
Natwest (NWG)	2006-2008	1,680,200%
First Solar (FSLR)	2006-2008	463.1%
Illumina (ILMN)	2006-2008	265.62%
Mastercard (MA)	2006-2008	257.64%
Booking (BKNG)	2006-2008	229.97%
CF Industries (CF)	2006-2008	225.65%
Deckers Outdoor (DECK)	2006-2008	180.34%
Agnico Eagle Mines (AEM)	2006-2008	157.13%
New Oriental Education & Technology (EDU)	2006-2008	149.59%
Sociedad Quimica y Minera de Chile SA ADR B (SQM)	2006-2008	148.03%
Credicorp (BAP)	2006-2008	139.74%
Intercontinental Exchange (ICE)	2006-2008	125.86%
Clean Harbors (CLH)	2006-2008	120.74%
Baidu (BIDU)	2006-2008	103.22%
Kinross Gold (KGC)	2006-2008	96.59%
McDonald’s (MCD)	2006-2008	96.14%
Elbit Systems (ESLT)	2006-2008	96.12%
Gilead Sciences (GILD)	2006-2008	92.98%
ICON (ICLR)	2006-2008	91.68%
Novo Nordisk A-S (NVO)	2006-2008	89.01%
Southern Copper (SCCO)	2006-2008	87.14%
Ambev SA ADR (ABEV)	2006-2008	86.11%
Alnylam Pharmaceuticals (ALNY)	2006-2008	84.69%
AAON (AAON)	2006-2008	82.31%
Stifel Financial (SF)	2006-2008	81.95%

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