Netflix (NFLX) had the highest return between 2012 and 2013 by a US stock in the S&P 500 (GSPC), returning 423.9%.

ASSET	YEARS	% RETURN
Netflix (NFLX)	2012-2013	423.86%
Tesla (TSLA)	2012-2013	419.81%
Regeneron Pharmaceuticals (REGN)	2012-2013	387.06%
Corpay (CPAY)	2012-2013	290.96%
Smurfit WestRock (SW)	2012-2013	281.83%
DexCom (DXCM)	2012-2013	271.95%
Gilead Sciences (GILD)	2012-2013	262.28%
Seagate Technology (STX)	2012-2013	261.93%
Builders FirstSource (BLDR)	2012-2013	239.52%
Incyte (INCY)	2012-2013	236.41%
Constellation Brands Inc Class A (STZ)	2012-2013	235.78%
Delta Air Lines (DAL)	2012-2013	235.49%
Tyler Technologies (TYL)	2012-2013	230.84%
Micron Technology (MU)	2012-2013	227.56%
Apollo Global Management LLC Class A (APO)	2012-2013	225.66%
PulteGroup (PHM)	2012-2013	217.56%
Axon Enterprise (AXON)	2012-2013	203.05%
Generac (GNRC)	2012-2013	200.55%
Diamondback Energy (FANG)	2012-2013	196.76%
NXP Semiconductors (NXPI)	2012-2013	191.06%
Huntington Ingalls Industries (HII)	2012-2013	185.6%
Marathon Petroleum (MPC)	2012-2013	178.06%
Aptiv (APTV)	2012-2013	175.74%
Western Digital (WDC)	2012-2013	175.46%
LyondellBasell Industries (LYB)	2012-2013	174.47%