At this point climate collapse and resource depletion is going to take care of us all by the end of the century so imo damage mitigation is our best option.
Don't have kids. Go vegan. Reduce your consumption of items produced by slavery and sweatshops as much as possible.
Basically just do as much as you can to lower the amount of suffering you create by existing.
Killing people in the name of left wing politics is going to make things worse for everyone.