  The particle nature of dark matter (DM) has been a long-lasting mystery. Many
models suggest that DM could decay or self annihilate into standard model
particles, and thus could be a source of gamma rays in the sky. The High
Altitude Water Cherenkov (HAWC) observatory has yielded some of the strongest
limits in searches of DM decay or annihilation. Building on the flux limits
provided by the HAWC collaboration in 2018, we consider the effects of
additional components from Galactic secondary Inverse-Compton scatterings and
extragalactic DM distributions. We find that these effects can significantly
improve the DM constraints, up to an order of magnitude in some cases. This
highlights the importance of considering secondary effects in detail in
LHAASO-WCDA and SWGO in the future.
