Killing four or five harmless NPCs (depending on current Character Tendency) will take you from Pure White to Pure Black. Below is a list of relatively harmless (won't hurt your game if dead) NPCs that you can kill to shift the character tendency.
1-1, 1-2, 1-3 - Dregling Merchant (-2)
2-1, 2-2 - Filthy Man (-3)
3-1 - Once Royal Mistress (-3)
4-1, 4-2 - Graverobber Blige (-2)
5-1, 5-2 - Filthy Woman (-1)
Nexus - Blue Phantom NPC the Crestfallen Warrior (-2). If you don't speak to him, he'll remain in the Nexus for the duration of the game, or until you kill him. If you exhaust his dialogues to "aggh who are you I don't remember" and reload he'll drop a Storied Soldiers Soul.
Nexus - Acolyte of God (-2) & Worshipper of God (-3), make sure you get the Pure Faintstone from her if your faith is at least 20 before you rescue Saint Urbain.
Nexus - Freke's Apprentice (-2). Make sure you have rescued Freke first.
Kill 3 of the special named NPCs. Killing these will also move the World Tendency -3 back towards black.
2-2 Body Form Scirvir the Wanderer (-2). Appears only in Pure White World Tendency
3-1 Blue Phantom Lord Rydell (-2). He has no Tendency requirement to appear, but requires Cell Key from Pure White World Tendency in 3-2.
5-2 Body Form Selen Vinland (-2). Appears only in Pure White World Tendency
En gros bute tout les vendeurs , ça te fait passer en pure black . Et sinon tu fais du PvP invasif .
----------------------------------------
So the world might be mended ....