Netflix (NFLX) had the highest return in January 2018 by a large-cap US stock, returning 37.8%.

ASSET	MONTH	% RETURN
Netflix (NFLX)	January 2018	37.84%
BeiGene (ONC)	January 2018	37.51%
Block (XYZ)	January 2018	35.19%
Stellantis (STLA)	January 2018	35.1%
Advanced Micro Devices (AMD)	January 2018	31.86%
Seagate Technology (STX)	January 2018	30.34%
Banco Bradesco S/A ADR (BBDO)	January 2018	28.87%
Petroleo Brasileiro Petrobras SA ADR (PBR)	January 2018	27.72%
Ecopetrol SA ADR (EC)	January 2018	26.9%
Pure Storage (PSTG)	January 2018	26.35%
Logitech International (LOGI)	January 2018	26.04%
Shopify (SHOP)	January 2018	25.92%
NVIDIA (NVDA)	January 2018	25.55%
Summit Therapeutics (SMMT)	January 2018	25.05%
Petróleo Brasileiro SA - Petrobras (PBR.A)	January 2018	24.02%
Tenet Healthcare (THC)	January 2018	23.8%
Amazon (AMZN)	January 2018	23.8%
SS&C Technologies (SSNC)	January 2018	23.6%
Itau Unibanco Banco (ITUB)	January 2018	23.22%
Keurig Dr Pepper (KDP)	January 2018	22.57%
argenx NV ADR (ARGX)	January 2018	22.21%
MercadoLibre (MELI)	January 2018	21.93%
Banco Bradesco SA ADR (BBD)	January 2018	21.05%
Texas Pacific Land Trust (TPL)	January 2018	20.41%
Boeing (BA)	January 2018	19.82%

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