Flutter Entertainment (FLUT) had the highest return in October 2009 by a large-cap US stock, returning 33%.

ASSET	MONTH	% RETURN
Flutter Entertainment (FLUT)	October 2009	32.99%
Amazon (AMZN)	October 2009	28.44%
Applied Digital (APLD)	October 2009	27.27%
Onto Innovation (ONTO)	October 2009	26.54%
Kratos Defense & Security Solutions (KTOS)	October 2009	23.22%
MicroStrategy (MSTR)	October 2009	22.19%
Smurfit WestRock (SW)	October 2009	18%
First Majestic Silver (AG)	October 2009	17.13%
Nomura Holdings Inc ADR (NMR)	October 2009	17%
Netflix (NFLX)	October 2009	16.85%
Moodys (MCO)	October 2009	15.74%
Fomento Economico Mexicano (FMX)	October 2009	15.62%
Akamai Technologies (AKAM)	October 2009	15.49%
Estee Lauder Companies (EL)	October 2009	15.33%
S&P Global (SPGI)	October 2009	14.84%
Manhattan Associates (MANH)	October 2009	14.52%
MSCI (MSCI)	October 2009	14.07%
Cheniere Energy Partners (CQP)	October 2009	13.89%
F5 Networks (FFIV)	October 2009	13.3%
CNH Industrial (CNH)	October 2009	13.08%
ConocoPhillips (COP)	October 2009	12.61%
Evercore Partners (EVR)	October 2009	12.55%
Kroger (KR)	October 2009	12.17%
Coca-Cola Femsa SAB de CV ADR (KOF)	October 2009	12.14%
L3Harris Technologies (LHX)	October 2009	11.61%

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