Amerant Bancorp (AMTB) had the highest return between 2016 and 2018 by a small-cap US stock, returning 4,080,166.7%.

ASSET	YEARS	% RETURN
Amerant Bancorp (AMTB)	2016-2018	4,080,166.67%
Immatics (IMTX)	2016-2018	195,900%
Delcath Systems (DCTH)	2016-2018	39,900%
Metalla Royalty & Streaming (MTA)	2016-2018	6,866.09%
Cronos (CRON)	2016-2018	6,159.04%
Gravity (GRVY)	2016-2018	2,505.59%
SIGA Technologies (SIGA)	2016-2018	1,581.14%
Thryv (THRY)	2016-2018	1,542.86%
Semler Scientific (SMLR)	2016-2018	1,304.08%
Canopy Growth (CGC)	2016-2018	1,159.73%
HIVE Blockchain Technologies (HIVE)	2016-2018	1,118.75%
TSS, Inc Common Stock (TSSI)	2016-2018	833.33%
eXp World (EXPI)	2016-2018	742.83%
EVI Industries (EVI)	2016-2018	710%
New Pacific Metals (NEWP)	2016-2018	692.86%
Amarin (AMRN)	2016-2018	631.72%
Mesabi Trust (MSB)	2016-2018	594.2%
Vericel Corp Ord (VCEL)	2016-2018	585.04%
Evotec SE ADR (EVO)	2016-2018	576.39%
Trilogy Metals (TMQ)	2016-2018	510.88%
Xpel (XPEL)	2016-2018	481.1%
Chemours (CC)	2016-2018	462.33%
Village Farms International (VFF)	2016-2018	459.59%
BioLife Solutions (BLFS)	2016-2018	454.38%
North American Construction (NOA)	2016-2018	445.37%

Small-cap stocks are treated as having a market cap between $300M and $2B.