expression
one instance reveals the whole; a single case tells you everything
Proverb meaning that a single example or action is representative of the whole; often used to judge character or patterns.
彼の遅刻は一事が万事だ。仕事の態度もだらしないに違いない。
His being late is a sign of the whole. His work attitude must be sloppy too.
一事が万事というから、小さなミスでも見逃せない。
As they say, one thing stands for everything, so even a small mistake can't be overlooked.