Different cultures at different times have had differing view on what constitutes good and evil.
For example, in earlier Roman times not worshiping the gods was evil as was insisting that this Jew from the Middle-East was the Son of God. Now of course, for many it's reversed.
So the question is whether there is something not culturally determined. From the perspective I hold, evil is the remnant of earlier good. One example is that slaughtering members of another tribe was good in its time and place but evil today.
Then to me the question is what beliefs and actions today further our biological and cultural evolution. We've seen from animal studies that cooperation and even sacrificing one's life can be positive as some animal research has shown.
Applying cultural evolution etc today leads me to the belief that today love, kindness, generosity, heroism and so forth are good. That makes hatred, unkindness, selfishness and cowardice evil.