Quick trick that I don’t think many know of because I’ve never come across a mention of it, we already know that killing an npc or black phantom with soulsucker or a status effect spell won’t change character tendency BUT all you need to do is strike the npc during their death animation for it to affect character tendency. Take
Black Phantom Selen Vinland for example, she’s pretty tough and who really wants to go through the trouble of fighting her in a swamp that prevents you from rolling while she attacks you with a weapon you can’t block ... aw man I really wish I could just sneak up behind her and use soulsucker for an easy kill but I need my CT to shift towards white, what a damn shame! Well don’t worry because all you have to do is hit her as soon as soulsucker empties her HP and boom it’s all good. Luckily, the game isn’t only checking for the source that emptied the enemies health bar but also if they were physically hit before the death animation finished and the souls dropped. This can save a lot of stress during a playthrough at least for me.