Aflac (AFL) had the highest return between February 15, 1984 and September 15, 1984 by a US stock with a market cap of $10B+, returning 38.6%.

ASSET	DATE	% RETURN
Aflac (AFL)	2/15/1984 - 9/15/1984	38.65%
Lockheed Martin (LMT)	2/15/1984 - 9/15/1984	34.84%
Walmart (WMT)	2/15/1984 - 9/15/1984	34.76%
General Dynamics (GD)	2/15/1984 - 9/15/1984	34.47%
Boeing (BA)	2/15/1984 - 9/15/1984	34.37%
McDonald’s (MCD)	2/15/1984 - 9/15/1984	32.48%
Northrop Grumman (NOC)	2/15/1984 - 9/15/1984	30.53%
Coca-Cola (KO)	2/15/1984 - 9/15/1984	29.25%
Crown (CCK)	2/15/1984 - 9/15/1984	28.57%
Raytheon Technologies (RTX)	2/15/1984 - 9/15/1984	27.52%
Altria (MO)	2/15/1984 - 9/15/1984	27.27%
Williams Companies (WMB)	2/15/1984 - 9/15/1984	24.26%
Walt Disney (DIS)	2/15/1984 - 9/15/1984	24.12%
Ball (BALL)	2/15/1984 - 9/15/1984	23.09%
Procter & Gamble (PG)	2/15/1984 - 9/15/1984	22.92%
British American Tobacco (BTI)	2/15/1984 - 9/15/1984	22.72%
Kellanova (K)	2/15/1984 - 9/15/1984	21.25%
Consolidated Edison (ED)	2/15/1984 - 9/15/1984	20.85%
Viatris (VTRS)	2/15/1984 - 9/15/1984	20.25%
American International (AIG)	2/15/1984 - 9/15/1984	19.05%
Avery Dennison (AVY)	2/15/1984 - 9/15/1984	18.75%
Watsco (WSO.B)	2/15/1984 - 9/15/1984	18.58%
Lowe's Companies (LOW)	2/15/1984 - 9/15/1984	17.7%
Genuine Parts (GPC)	2/15/1984 - 9/15/1984	17.36%
Revvity (RVTY)	2/15/1984 - 9/15/1984	16.61%