The classic alignment grid consisting of three rows (Good, Neutral, and Evil) and three columns (Lawful, Neutral, and Chaotic) is a contentious topic in TTRPGs. A lot of games (including the Tales of the Valiant RPG) don’t use it, but it endures. Criticisms include that the system is too rigid a
Same way you do it with any creature. Make it racist. Unicorns superior to all, look down on other races with contempt and wonton disregard for their lives.