Electron capture supernovae (ECSNe) are considered the main source of low-velocity neutron stars, which in turn are important for the formation of double neutron star systems. I will review recent work suggesting that a large fraction of ECSNe may produce thermonuclear explosions instead of neutron stars. I will then discuss how a subset of core-collapse supernovae with subsonic ejecta may serve as an alternative source of low-velocity neutron stars and highly-asymmetric BH/BH and NS/BH mergers, such as those recently seen by LIGO/Virgo.