始乱终弃的英文是「first he abused her and in the end he gave her up」
shi luan zhong qi
乱:淫乱,玩弄。先乱搞,后遗弃。指玩弄女性的恶劣行径。
唐·元稹《莺莺传》:“始乱之,终弃之。”