Two celebrities recently sustained injuries to their nails. Catherine Zeta-Jones had her toenail torn off when a crew member stepped on her foot. This incident is probably worse than Mariah Carey, who kept the organizers of an awards ceremony waiting for 90 minutes because she had broken a fingernail.

The third sentence contains a faulty comparison. The phrase "worse than" indicates the presence of a comparison, but the two items that are compared are an incident (Catherine's toenail being torn off) and a person (Mariah). This comparison is not logical. Incidents should be compared to incidents, and people should be compared to people.

Catherine Zeta-Jones had her toenail torn off when a crew member stepped on her foot. This incident is probably worse than Mariah Carey's experience: the singer kept the organizers of an awards ceremony waiting for 90 minutes because she had broken a fingernail.

This revision compares an incident with an experience; this is a logical comparison.

Catherine Zeta-Jones had her toenail torn off when a crew member stepped on her foot. She probably suffered more than Mariah Carey, who kept the organizers of an awards ceremony waiting for 90 minutes because she had broken a fingernail.

This revision compares Catherine to Mariah, which is logical as well.