Based on the level of respect or formality, you can say "I hate that." in Korean in 3 ways:

• Informal: jeogeot-i sileo. (저것이 싫어.)
• Formal: na-neun jeogeot-i sileoyo. (나는 저것이 싫어요.)
• Very formal: jeo-neun jeogeot-i silsseumnida. (저는 저것이 싫습니다.)