I will only list a few and only the easiest.
Stop mining gold
Stop making yachts
Stop building mansions
Stop making supercars (even electric supercars)
None of these activities can be defended against the harm they cause. They cause both environmental and social harm and provide little to no redeeming value.
We should probably put a moratorium on space exploration. The near-term benefits are too small compared to the resources they consume. We should continue to put up useful satellites, but deep space probes or exploration and experimentation should wait until we have secured our planetary future. The smart and capable people doing space exploration should instead consider working on more pressing problems.
These things governments could stop with little fuss. Maybe we phase them out not go cold turkey but stopped they should be.
Stop Wars and Violence. I understand this is currently not actionable.
This is hard to near impossible but the waste suffering, and destruction is appalling.
Stop making bombs, I don’t care if you are a terrorist or a super power. Just cut it out. Don’t make them, don’t use them and turn the ones you have into something useful or at least something not harmful.
If you are a person or country that causes other to fear, causes them to feel a need to create a defense, stop spreading fear.