1. Add insult to injury 
The phrase “add insult to injury” is a common English idiom. It means to make a bad situation worse. This phrase is usually used as part of a sentence.
Here are three example sentences for your reference.
“They told me I didn’t have enough experience, and to add insult to injury, they hired my friend who had similar qualifications as me. “
“First, he missed his bus, and to add insult to injury, it started pouring. “
“Only five people came to his party, and to add insult to injury, some left before it was over.”

2. Once in a blue moon
Another English phrase is “once in a blue moon.” It is often used as part of a sentence. This phrase is used as another way to say rarely.
Here are three example sentences for your reference.
“She gets drunk once in a blue moon.”
“A chance like this comes once in a blue moon!”
“You find a rare item like this once in a blue moon.”