Chink in (one's)/the armor American British informal
To indicate a minor yet extremely damaging fault or weakness
Jane is bright but his hot temper has wrecked many business relationships. It's a chink in his armor.
Chemistry has always been a chink in my armor.
The senior's tendency to use the money to buy many new houses was the chink in the armor the police needed to accuse him of corruption.
Something that makes spectators excited and delighted
The garden, full of colourful flowers is a joy to behold.