Amazon (AMZN) had the highest return between 1996 and 1998 by a mega-cap US stock, returning 2,096.1%.

ASSET	YEARS	% RETURN
Amazon (AMZN)	1996-1998	2,096.14%
Microsoft (MSFT)	1996-1998	531.29%
Cisco Systems (CSCO)	1996-1998	460.6%
Costco Wholesale (COST)	1996-1998	373.37%
International Business Machines (IBM)	1996-1998	314.62%
Home Depot (HD)	1996-1998	290.84%
Walmart Inc Common Stock (WMT)	1996-1998	273.88%
ASML Holding NV ADR (ASML)	1996-1998	254.91%
Eli Lilly and (LLY)	1996-1998	232.94%
Morgan Stanley (MS)	1996-1998	226.58%
GE Aerospace (GE)	1996-1998	201.32%
SAP SE ADR (SAP)	1996-1998	200.84%
JPMorgan Chase (JPM)	1996-1998	167.23%
Wells Fargo (WFC)	1996-1998	158.44%
American Express (AXP)	1996-1998	157.07%
Abbott Laboratories (ABT)	1996-1998	151.9%
Citigroup (C)	1996-1998	148.27%
Raytheon Technologies (RTX)	1996-1998	144.18%
AstraZeneca PLC ADR (AZN)	1996-1998	144.13%
Merck (MRK)	1996-1998	140.76%
Royal Bank of Canada (RY)	1996-1998	136.81%
Procter & Gamble (PG)	1996-1998	132.97%
Oracle (ORCL)	1996-1998	126.97%
Berkshire Hathaway (BRK.A)	1996-1998	118.75%
Applied Materials (AMAT)	1996-1998	114.78%

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