  From 16 years of INTEGRAL/SPI $\gamma$-ray observations, we derive bounds on
annihilating light dark matter particles in the halo of the Milky Way up to
masses of about 300 MeV. We test four different spatial templates for the dark
matter halo, including a Navarro-Frenk-White (NFW), Einasto, Burkert, and
isothermal sphere profile, as well as three different models for the underlying
diffuse Inverse Compton emission. We find that the bounds on the s-wave
velocity-averaged annihilation cross sections for both the electron-positron
and the photon-photon final states are the strongest to date from $\gamma$-ray
observations alone in the mass range $\lesssim 6$ MeV. We provide fitting
formulae for the upper limits and discuss their dependences on the halo
profile. The bounds on the two-photon final state are superseding the limits
from the Cosmic Microwave Background in the range of 50 keV up to $\sim 3$ MeV,
showing the great potential future MeV mission will have in probing light dark
matter.
