Advanced Micro Devices (AMD) had the highest return in August 1993 by a mega-cap US stock, returning 33.5%.

ASSET	MONTH	% RETURN
Advanced Micro Devices (AMD)	August 1993	33.5%
Costco Wholesale (COST)	August 1993	19.68%
Shell PLC ADR (SHEL)	August 1993	17.91%
Micron Technology (MU)	August 1993	17.63%
AstraZeneca PLC ADR (AZN)	August 1993	12.84%
Thermo Fisher Scientific (TMO)	August 1993	12.31%
Johnson & Johnson (JNJ)	August 1993	12.06%
Berkshire Hathaway (BRK.A)	August 1993	9.53%
Caterpillar (CAT)	August 1993	7.34%
Chevron (CVX)	August 1993	6.87%
Raytheon Technologies (RTX)	August 1993	5.64%
Morgan Stanley (MS)	August 1993	4.98%
McDonald’s (MCD)	August 1993	4.83%
Merck (MRK)	August 1993	4.08%
Abbott Laboratories (ABT)	August 1993	4%
Eli Lilly and (LLY)	August 1993	3.77%
International Business Machines (IBM)	August 1993	3.68%
Bank of America (BAC)	August 1993	3.59%
Toyota Motor Corporation ADR (TM)	August 1993	3.23%
Oracle (ORCL)	August 1993	2.74%
Novo Nordisk A-S (NVO)	August 1993	1.51%
Wells Fargo (WFC)	August 1993	1.43%
Walmart (WMT)	August 1993	1.11%
Microsoft (MSFT)	August 1993	0.5%
Coca-Cola (KO)	August 1993	0%

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