He was caught off guard by a sucker punch to the stomach.
sucker bet
Frequency:
40
%
He knew it was a sucker bet, but he couldn't resist the temptation.
Idiomatic Expressions for sucker
Phrase: sucker for punishment
Meaning: someone who repeatedly puts themselves in difficult or painful situations
Usage: She keeps going back to that toxic relationship, she's a real sucker for punishment.