"strong recommendation" is "강추"(kang-chu) in Korean.
The Gangchu (강추), is compound of 강력 (powerful) + 추천 an abbreviation for (recommendation).So it means violently recommended, meaning a strong recommendation.

※ The antonym is 비추(Bichu), an abbreviation of 비 (non, bi) + 추천 (recommendation, Chucheon). It means the opposite of 강추(Gang-chu), meaning “not recommended”.