1. in a way that causes or results in death
2. in a way that has a destructive or ruinous effect; disastrously

Examples

• He was fatally wounded in the accident.
• The company was fatally flawed in its business strategy.
• The disease proved to be fatally contagious.
• Her decision to ignore the warning was fatally mistaken.
• The scandal fatally damaged his political career.
• The patient was fatally ill and had only weeks to live.