Tompkins Financial (TMP) had the lowest return in October 1986 by a US stock, returning -50%.

ASSET	MONTH	% RETURN
Tompkins Financial (TMP)	October 1986	-50%
CEL-SCI (CVM)	October 1986	-39.53%
Universal Health Services (UHS)	October 1986	-39.4%
Spectrum Brands (SPB)	October 1986	-32.14%
Research Frontiers (REFR)	October 1986	-26.98%
Monster Beverage (MNST)	October 1986	-23.52%
Cadiz (CDZI)	October 1986	-22.03%
Arrow Electronics (ARW)	October 1986	-21.57%
Koninklijke Philips NV ADR (PHG)	October 1986	-20.63%
RF Industries (RFIL)	October 1986	-20.21%
Avis Budget (CAR)	October 1986	-20%
Johnson Controls International (JCI)	October 1986	-20%
Mount Logan Capital Inc Common Stock (MLCI)	October 1986	-20%
Oceaneering International (OII)	October 1986	-19.99%
McEwen Mining (MUX)	October 1986	-19.35%
Gencor Industries (GENC)	October 1986	-19.18%
Powell Industries (POWL)	October 1986	-18.75%
Repligen (RGEN)	October 1986	-18.75%
Micron Technology (MU)	October 1986	-18.56%
Quanex Building Products (NX)	October 1986	-18.42%
CECO Environmental (CECO)	October 1986	-18.33%
Tidewater (TDW)	October 1986	-17.95%
Bridgford Foods (BRID)	October 1986	-17.93%
Hasbro (HAS)	October 1986	-17.34%
Suncor Energy (SU)	October 1986	-17.22%