UnitedHealth (UNH) had the highest return in March 2025 by a mega-cap US stock, returning 10.9%.

ASSET	MONTH	% RETURN
UnitedHealth (UNH)	March 2025	10.88%
Mitsubishi UFJ Financial Group Inc ADR (MUFG)	March 2025	7.23%
Shell PLC ADR (SHEL)	March 2025	7.1%
Exxon Mobil (XOM)	March 2025	6.47%
TotalEnergies SE ADR (TTE)	March 2025	6.47%
Novartis AG ADR (NVS)	March 2025	5.4%
Chevron (CVX)	March 2025	4.91%
Philip Morris International (PM)	March 2025	3.43%
Berkshire Hathaway (BRK.B)	March 2025	3.17%
Berkshire Hathaway (BRK.A)	March 2025	2.94%
Coca-Cola (KO)	March 2025	2.72%
Advanced Micro Devices (AMD)	March 2025	1.2%
Johnson & Johnson (JNJ)	March 2025	0.53%
PepsiCo (PEP)	March 2025	-0.06%
AbbVie (ABBV)	March 2025	-0.22%
LIN TV (LIN)	March 2025	-0.41%
BHP (BHP)	March 2025	-0.93%
T-Mobile US (TMUS)	March 2025	-0.96%
Alibaba (BABA)	March 2025	-1.33%
Merck (MRK)	March 2025	-1.36%
Raytheon Technologies (RTX)	March 2025	-1.4%
Sandisk (SNDK)	March 2025	-1.81%
Procter & Gamble (PG)	March 2025	-1.82%
International Business Machines (IBM)	March 2025	-2.39%
HSBC Holdings PLC ADR (HSBC)	March 2025	-2.55%

Mega-cap stocks are treated as having a market cap of $200B+.