Analysis:
This quatrain by Saadi Shirazi paints a poignant picture of heartbreak and loss. Let's delve into the deeper meanings:

Betrayal and Heartbreak: The poet expresses deep sorrow over the loss of a loved one who has betrayed them. The "sword of injustice" symbolizes the pain caused by this betrayal.
Diminished Radiance: The return of the beloved is marked by a loss of their former allure. This suggests that the betrayal has tarnished their image in the poet's eyes.
Self-Inflicted Wound: The phrase "having brought upon themselves the inscription" suggests that the beloved has brought about their own downfall through their actions.
Sense of Power: The poet seems to have gained a sense of power or satisfaction from the beloved's downfall, even though they are still deeply hurt.

Themes:

Betrayal and heartbreak
Loss of love
Sense of power
Justice and karma

Deeper Meaning:
This quatrain explores complex emotions related to love, loss, and betrayal. The poet's sense of satisfaction at the beloved's downfall is a complex emotion that may arise from a desire for justice or a need to protect oneself from further hurt. The quatrain suggests that even in the midst of great pain, there can be a sense of empowerment.

This quatrain is a powerful exploration of human emotions and the complexities of relationships. It reminds us that betrayal can leave deep wounds, but it can also lead to a sense of personal growth and resilience.