woe betide someone idiom
（某人）要倒霉（或遭殃）
said when there will be trouble for someone, or someone will be punished, if they do a particular thing
This is the second time he's been sent home from school this month, so woe betide him if it happens again! 这是他本月内第二次被从学校赶回了家，要是再发生一次这样的事，他就要倒霉了。