While in Warhammer 40k ALL FACTIONS ARE BAD, the Chaos are the bad of the bad. The Sisters of Battle may have literal angels who play on their part, but Chaos is literal daemons. Where Space Marines may get out of hand and kill innocents, Khorne is so aggressive for blood that his lieutenant Kharn the Betrayer will literally slaughter his own World Eaters just because he’s so anxious to kill and maim and destroy–more blood for the blood god. Getting started in Chaos is fun.