If you marry someone who only shows you their good side, they will make a 180 degree turn after you get married and end up harassing you psychologically.
この場合、次のような言い方ができますよ。
ーIf you marry someone who only shows you their good side, they will make a 180 degree turn after you get married and end up harassing you psychologically.
「良い一面しか見せない人と結婚したら、結婚した後豹変してモラハラされるよ」
to make a 180 degree turn で「豹変する」
to harass someone psychologically で「人にモラハラをする」
ご参考まで！
カナダ 
