expression
of all things; of all people; of all places
Expresses surprise, disbelief, or criticism that something or someone is the last thing you would expect in a given situation. Often used as a set phrase at the beginning of a sentence.
事もあろうに、彼は会議中に居眠りを始めた。
Of all things, he started dozing off during the meeting.
事もあろうに、こんな大事な日に限って電車が遅れるなんて。
Of all days, the train had to be late on such an important day.