Antonyms for "even tempers" would be words that describe people who are easily agitated or have a tendency to lose their cool. Such words might include "irritable," "short-tempered," "hot-headed," "impulsive," or "volatile." People with these characteristics might be prone to outbursts of anger or frustration and have difficulty controlling their emotions. Conversely, people with even tempers are calm, patient, and slow to anger. They are able to handle stressful situations with grace and composure, and are often appreciated for their ability to maintain a stable and level-headed demeanor.