General:
* Perceptive: This implies a keen understanding of people's feelings.
* Intuitive: This suggests a strong gut feeling or instinct about emotions.
* Empathetic: This highlights a deep understanding and connection to others' emotions.
* Sensitive: This describes being easily affected by and aware of emotions.
More specific:
* Discerning: This implies a refined and accurate ability to read emotions.
* Astute: This suggests intelligence and shrewdness in understanding emotions.
* Insightful: This emphasizes a deep understanding of emotions and their underlying causes.
* Observant: This emphasizes the ability to pick up on subtle emotional cues.
Informal:
* Sharp: This suggests a quick and keen understanding of emotions.
* Savvy: This implies experience and wisdom in understanding emotions.
Ultimately, the best adjective depends on the context and the specific kind of emotional understanding you want to highlight.