Applied Digital (APLD) has had the highest return this decade by a mid-cap US stock, returning 34,159.3%.

ASSET	DECADE	% RETURN
Applied Digital (APLD)	2020s	34,159.26%
Regencell Bioscience (RGC)	2020s	4,149.53%
Centrus Energy (LEU)	2020s	2,624.42%
Sezzle Inc Common Stock (SEZL)	2020s	2,341.59%
Sterling Construction (STRL)	2020s	1,950.98%
Alpha Metallurgical Resources (AMR)	2020s	1,846.85%
Verona Pharma PLC ADR (VRNA)	2020s	1,788.69%
Modine Manufacturing (MOD)	2020s	1,714.6%
Trump Media & Technology (DJTWW)	2020s	1,677.86%
IES (IESC)	2020s	1,239.73%
Triumph (TGI)	2020s	1,056.05%
Power Solutions International, Inc Common Stock (PSIX)	2020s	1,030.88%
Uranium Energy (UEC)	2020s	998.92%
Tecnoglass (TGLS)	2020s	969.8%
Riot Blockchain (RIOT)	2020s	916.67%
Anbio Biotechnology Class A Ordinary Shares (NNNN)	2020s	823.19%
Dillards (DDS)	2020s	741.17%
Sitime (SITM)	2020s	739.38%
Hawkins (HWKN)	2020s	734.36%
Indivior PLC Ordinary Shares (INDV)	2020s	714.54%
Protagonist Therapeutics (PTGX)	2020s	700%
Camtek (CAMT)	2020s	696.25%
Stride (LRN)	2020s	671.69%
ELF Beauty (ELF)	2020s	657.36%
Calix (CALX)	2020s	635.5%

Mid-cap stocks are treated as having a market cap between $2B and $10B.