  We present a comprehensive multiwavelength investigation into flares and
activity in nearby M~dwarf stars. We leverage the most extensive
contemporaneous dataset obtained through the Transiting Exoplanet Sky Survey
(TESS), Kepler/K2, the Neil Gehrels Swift Observatory (\textit{Swift}), and the
Hubble Space Telescope (HST), spanning the optical and near-ultraviolet (NUV)
regimes. In total, we observed 213 NUV flares on 24 nearby M dwarfs, with
$\sim$27\% of them having detected optical counterparts, and found that all
optical flares had NUV counterparts. We explore NUV/optical energy
fractionation in M dwarf flares. Our findings reveal a slight decrease in the
ratio of optical to NUV energies with increasing NUV energies, a trend in
agreement with prior investigations on G-K stars' flares at higher energies.
Our analysis yields an average NUV fraction of flaring time for M0-M3 dwarfs of
2.1\%, while for M4-M6 dwarfs, it is 5\%. We present an empirical relationship
between NUV and optical flare energies and compare to predictions from
radiative-hydrodynamic and blackbody models. We conducted a comparison of the
flare frequency distribution (FFDs) of NUV and optical flares, revealing the
FFDs of both NUV and optical flares exhibit comparable slopes across all
spectral subtypes. NUV flares on stars affect the atmospheric chemistry, the
radiation environment, and the overall potential to sustain life on any
exoplanets they host. We find that early and mid-M dwarfs (M0-M5) have the
potential to generate NUV flares capable of initiating abiogenesis.
