Retreating is not necessarily a way to avoid suffering.
In the previous section, it was shown that the enemy would perceive Arjuna's withdrawal as being due to fear. Furthermore, Krishna states that the enemy will belittle his power and use words that should not be spoken face-to-face.
This is not a general principle that encourages people to live dominated by the criticism of others. It suggests that deviating from one's proper duties does not necessarily lead to peace of mind, and in specific situations like a battlefield, it may bring about another great suffering. Even inaction has real consequences.
Japanese Translation from the Geeta Press Edition - Chapter 2, Section 36: "There is nothing more painful than being blamed by an enemy."
Sanskrit original text
अवाच्यवादांश्च बहून्वदिष्यन्ति तवाहिताः ।
निन्दन्तस्तव सामर्थ्यं ततो दुःखतरं नु किम् ॥ ३६ ॥Romanization
avācyavādāṃś ca bahūn vadiṣyanti tavāhitāḥ |
nindantas tava sāmarthyaṃ tato duḥkhataraṃ nu kim || 36 ||And your enemies will despise your power, and they will speak many words that should not be said. What could possibly be more difficult than this? (36)
In section 34, it described the "dishonor" that is permanently spoken by ordinary people. On the other hand, this section describes the words of condemnation spoken by an enemy like Duryodhana in front of Arjuna.
Scandals and disgrace in the world cause intense sadness and pain only to those who have honor and status, and do not affect everyone equally. However, accusations and condemnations spoken directly by enemies can cause great suffering even to ordinary people.
Therefore, the speaker points out the following: The damage that Arjuna suffers is not only losing fame worldwide or damaging his reputation among friends who held him in high regard as a hero. Enemies like Duryodhana are always trying to harm him and rejoice in seeing him suffer. They will now come forward and criticize his valor, strength, and combat skills, showering him with many derogatory words that should not be said. They will loudly proclaim that Arjuna is not a warrior but was effeminate from the moment he was born. And they will also denigrate his Gandiva bow and his valor in the same way.
By pointing out that there is nothing more painful than this, the Lord aimed to reveal Arjuna's misunderstanding: that his happiness lies in stopping the fighting, and that participating in the fight will bring sorrow.
The Lord made it clear through these arguments that retreating from the battle would be the greatest source of suffering for him.