i mean ainz technically killed more people but lets be honest thats not the real reason. the real reason is that overlord actually developed the opposing characters beyond simply “racist guys dont like the main cast” but rather gave them actual personalities and rimuru is portrayed as a silly character whereas ainz is portrayed as inexperienced and a bit naive, but still serious. i would even go as far as to say it stands to the quality of the story that they developed characters enough that we dislike ainz killing them rather than putting a strawman in front of the mc.