Argenx NV ADR (ARGX) had the highest return in December 2017 by a large-cap US stock, returning 99.4%.

ASSET	MONTH	% RETURN
argenx NV ADR (ARGX)	December 2017	99.43%
Freeport-McMoran Copper & Gold (FCX)	December 2017	36.01%
Teva Pharma Industries Ltd ADR (TEVA)	December 2017	27.27%
Ecopetrol SA ADR (EC)	December 2017	25.26%
BeiGene (ONC)	December 2017	21.74%
Floor & Decor (FND)	December 2017	20.58%
Carvana (CVNA)	December 2017	18.76%
DaVita HealthCare Partners (DVA)	December 2017	18.44%
Warner Bros Discovery (WBD)	December 2017	18.41%
Roku (ROKU)	December 2017	18.38%
Lululemon Athletica (LULU)	December 2017	17.68%
Suzano Papel e Celulose SA ADR (SUZ)	December 2017	17.53%
Akamai Technologies (AKAM)	December 2017	17.34%
Halliburton (HAL)	December 2017	17.2%
Banco De Chile (BCH)	December 2017	16.6%
Burlington Stores (BURL)	December 2017	16.13%
XPO Logistics (XPO)	December 2017	16.02%
Best Buy (BBY)	December 2017	15.23%
MercadoLibre (MELI)	December 2017	15.09%
Brown-Forman (BF.B)	December 2017	14.82%
Diamondback Energy (FANG)	December 2017	14.61%
Nordson (NDSN)	December 2017	14.59%
Grupo Financiero Galicia SA ADR (GGAL)	December 2017	14.58%
Viatris (VTRS)	December 2017	14.44%
Banco Santander Chile (BSAC)	December 2017	14.42%

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