Is there any plausible astronomical source of energy that could wipe out humanity without rendering the planet inhabitable? I'm aware of hard radiations from space can wipe out life but I believe that would also causes the planet to be inhabitable for a period of time. Is there any other kind of energetic astronomical event that could destroy life through a transient pulse of radiation (particles or photons) without any "cool down" needed for new life to develop?

The event could be known or theoretical or just plausible that spans entire galaxy if necessary.
The cockroach and the tardigrade can withstand just about anything.  Next, any radiation blast consisting of wavelengths reasonably attenuated with water wouldn't affect, directly at least, all the deep-sea creatures.