Canto 2 -
Ayodhyā-kāṇḍa
Chapter 35: Furious Sumantra Criticizes Kaikeyī
Text 2.35.7
यन्महेन्द्रमिवाजय्यं दुष्प्रकम्प्यमिवाचलम्।
महोदधिमिवाक्षोभ्यं सन्तापयसि कर्मभिः॥
yan mahendram ivājayyaṁ duṣprakampyam ivācalam
mahodadhim ivākṣobhyaṁ santāpayasi karmabhiḥ
yat = your; mahā-indram = the great Indra; iva = like; ajayyam = who is unconquerable; duṣprakampyam = immovable; iva = like; acalam = a mountain; mahā-udadhim = a great ocean; iva = like; akṣobhyam = and imperturbable; santāpayasi = you torment; karmabhiḥ = by activities.
By your activities you torment [the king] who is unconquerable like the great Indra, immovable like a mountain and imperturbable like a great ocean.1
1 Mahodadhim ivākṣobhyam indicates that under normal circumstances King Daśaratha could not be perturbed and thus resembled a great ocean.
This is another argument.