  Stellar flares have been extensively studied in soft X-rays (SXR) by
basically every X-ray mission. Hard X-ray (HXR) emission from stellar
superflares, however, have only been detected from a handful of objects over
the past years. One very extreme event was the superflare from the young
M-dwarf DG CVn binary star system, which triggered Swift/BAT as if it was a
$\gamma$-ray burst (GRB). In this work, we estimate the expected $\gamma$-ray
emission from DG CVn and the most extreme stellar flares by extrapolating from
solar flares based on measured solar energetic particles (SEPs), as well as
thermal and non-thermal emission properties. We find that ions are plausibly
accelerated in stellar superflares to 100 GeV energies, and possibly up to TeV
energies in the associated coronal mass ejections. The corresponding
$\pi^0$-decay $\gamma$-ray emission could be detectable from stellar
superflares with ground-based $\gamma$-ray telescopes. On the other hand, the
detection of $\gamma$-ray emission implies particle densities high enough that
ions suffer significant losses due to inelastic proton-proton scattering. The
next-generation Cherenkov Telescope Array (CTA) should be able to probe
superflares from M-dwarfs in the solar neighbourhood and constrain the energy
in interacting cosmic rays and/or their maximum energy. The detection of
$\gamma$-ray emission from stellar flares would open a new window for the study
of stellar physics, the underlying physical processes in flares and their
impact on habitability of planetary systems.
