Woe betide anyone who touches my lunch in the fridge.
woe betide
idiomUsed to warn someone that trouble will occur if that person does something: bad things will happen to.
Origin
disputed originFrom Early Modern English woe (“great sadness or distress; calamity, trouble”) + betide (“to happen to, befall”), formerly used to decry a person’s actions. Grammatically, the verb is in the subjunctive mood.
The boss is in a terrible mood today, so woe betide the employee who arrives late for the meeting.
Woe betide the traveler who ignores the local warnings, for the mountain path becomes treacherous and unforgiving once the sun sets.