All the careful arguments fall away, and what remains is raw grief. Arjuna cries out: Alas! What a terrible sin we are prepared to commit! Driven by greed for a kingdom and its pleasures, we stand ready to kill our own people!
The words 'aho bata' are a cry of anguish and disbelief — the kind of exclamation a person makes when they suddenly see the full weight of what they are about to do. It is the moment of reckoning: 'What have we become? What are we doing?'
Notice that Arjuna says 'vayam' — we — not just 'I'. He does not point the finger only at the Kauravas. He includes himself and the entire Pandava side in the blame. In his eyes, both sides share the guilt equally. The greed for royal pleasures — 'rajya-sukha-lobha' — is the same disease he accused the Kauravas of in verse 1.38. Now he turns the diagnosis on himself.