In Sundarakāṇḍa (38) a celestial crow (son of Indradeva) in…

To summarize the event. This incident happens on the Chitrakūṭa mountain. The crow is a celestial son of Indradeva. He does not leave Sītā alone despite her numerous attempts to ward him away. He eats the flesh of her bossom, pierces them with his sharp claws...+

Lord Rāma (whose lap Sītā was sleeping on) wakes up and sees the the torn bossom of Sītā. Upon finding the crow was guilty, he releases a brahmāstra on him. The crow tries to seek shelter but all the devas turn him away. He comes back to Rāma & falls on his feet..+

..he is spared by the lord but he has to loose one eye because a brahmāstra once casted cannot be taken back. (मोघम् कर्तुम् न शक्यम् तु ब्राह्मम् अस्त्रम्).

Now, why was this? Let us see the exegesis of Achārya Parāśara Bhaṭṭa of this incident.

Both the celestial crow & rāvaṇa transgressed against the Goddess. But the crow's transgression was unique because it was in the presence of the divine couple of Rāma-Sītā together. Due to the mere sannidhi (proximity) of the divine mother - Bhagavān bestowed his grace.

The divine mother, sītā mā, is the puruṣakāra (mediator) in the ontological relationship between Bhagavān and the Jīva. Just like a mother intermediates in a dispute between the father and her son to seek the father's mercy for the salvation of the son.

Now, Shishya Nāñciyar objects and says - maybe the grace was bestowed because the crow took refugee of Bhagavān? Acharya Bhaṭṭa says this is not so. The crow first ran away, then he took refugee of all the Gods. They abandoned him. Only as a last resort does the crow go to Rāma

The crow hurt Goddess Sita more than Ravana physically speaking. He made her bleed, he ate flesh from her bossom. He transgressed *more* than Rāvaṇa but only Rāvaṇa was beheaded while the crow only had his right eye blinded. But why is the Goddess having this effect?

It is because of her daurbalyatā (tenderness) & utter inability to see another jīva in pain. The divine mother cannot tolerate any soul hurting & bhagawān knows this. A prime example of this is seen when she asks Hanuman to forgive the rākṣasī-s guarding her in lanka from death

The Goddess not only pleads for mercy on behalf of the raakShasii-s here but she tells Hanuman that it is those who sin the most who need our mercy the most. It is the man who is the most lost who needs divine grace the most. Not the virtuous man who already follows dharma.

It is the dirty who require a bath. Not the ones who already smell like fragrance. She tells the vaanara

न परः पापमादत्ते परेषां पापकर्मणाम्
समयो रक्षितव्यस्तु सन्तश्चारित्रभूषणाः

"The gracious do not repay the sin of sinners with sin. Never not adhere to this rule."

पापानां वा शुभानां वा वधार्हाणां प्लवंगम
कार्यं कारुण्यमार्येण न कश्चिन्नापराध्यति

"O vaanara, the gracious and noble men repay the wages of sin with compassion. For there is none amongst us who is entirely sinless. Do not loose compassion even for those deserving to die"

मैवं वद महाबाहो दैवी ह्येषा परा गतिः |
प्राप्तव्यं तु दशा योगान्मयैतदिति निश्चितम्
दासीनां रावणस्याहं मर्षयामीह दुर्बला

"It was divine motherly destiny to obtain this position of pleadinh for the mercy of these raakShasi daasi-s to you. I am tender. I will forgive them."

Here, we see sita mata not only admits she is tender and weak in these matters (durbalaa) but by her leela through her daivadashaa she wants to be in the position of being able to seek forgiveness for these jivas.

From the Teṅkalai position which Acharya Bhaṭṭa naturally holds, the unconditional spontaneous unwarranted boon of divine grace is the last resort, the tantum sanctum of sinners who have no other resort left.