weak spot (noun)

1. Her heart was always his weak spot; he had the power to break it with a single word.

2. The large window in the living room was the weak spot in the design, as it let in too much sunlight and made the room uncomfortably warm.

3. The comedian's weak spot was his own clumsiness; he would often incorporate hilarious falls and mishaps into his stand-up routine.

4. According to Greek mythology, Achilles' weak spot was his heel, which ultimately led to his downfall in the Trojan War.