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

• Informal: na-neun ni-ga geureokke mal-hal jul alatseo (나는 니가 그렇게 말할 줄 알았어)
• Formal: jeo-neun dangsin-i geureokke mal-hal jul alatseo (저는 당신이 그렇게 말 할줄 알았어요), jeo-neun dangsin-i geureokke mal-hal jul alatseupnida (저는 당신이 그렇게 말할 줄 알았습니다)
• Very Formal: jeo-neun dangsin-ggeseo geureokke malsseum-hasil jul alatseupnida (저는 당신이 그렇게 말씀 하실줄 알았습니다)

- I: na-neun (나는), jeo-neun (저는)
- to know: alda (알다)
- you (subjective): ne-ga (네가), ni-ga (니가), neo-neun (너는), dangsin-eun (당신은), dansin-ggeseo-neun (당신께서는) - omitted here
- to say: mal-hada (말하다), malsseum-hada (말씀하다)
- that (objective): jeogeot-eul (저것), geureokke (저렇게)

Please refer to How to pronounce Korean Alphabet for the English pronunciation in this answer.