It can be anything.
#1
#1 Humans have space traveled etc etc. Anyways, they have found a way to make anything by using star atoms. But they need to blow up stars for it. Some aliens didnt like that, so now were at war.
#2 Genetic Science has evolved, you can change your dna, implement animal dna into you etc. This one man made a genetic copy variant of himself for a son. Someone took his son, so he goes full on john wick
#3 A scythe fan fic. Scythe Grimm has tooken it upon himself to make the Scythe City. A lot of people stand in his way, but then again: you cant stand without legs.
3points