The last time something like this happened was when his wife and children died in a muggle terrorist suicide attack. Both magical and mundane governments had turned utterly useless, and he had to take things into his own hands again, leaving hundreds of corpses behind, destroying the organisation responsible to the last man, together with every direct supporter, as a dire and bloody warning. He could get away with killing magical terrorists, but apparently, disposing of the muggle ones proved unacceptable. ICW and Magical Britain had declared him a dark lord. Harry had no fear of either and could easily take them on at this point. While they were morons, he did have some former friends and acquaintances in both organisations, so he decided not to bother with them at all. What was the point anyway? With nothing left for him in Wizarding Britain, he simply changed his identity and travelled around the world exploring magic.