• katamena karmaṇā — by what action
  Katama (which one of many) + karman. Karma is the Bhāgavata's standard idiom for whatever produced this body. Kṛṣṇa narrows the question to action because the lesson He intends to draw is about a specific act.
• atat - arhaḥ — undeserving of this
  A- (not) + tat (this) + arha (deserving). Kṛṣṇa's diagnosis is already in His question: this fall does not match the soul's piety. The mismatch is precisely what aparādha produces — disproportionate disgrace from a small wrong against the right person.
• su - bhadra — O good soul
  Su (good) + bhadra (auspicious). The poet keeps Kṛṣṇa addressing Nṛga as bhadra throughout — pre-emptive vindication. The fall was real; the soul was never lost.
• yat manyase naḥ kṣamam — if you think it appropriate
  Kṣama here means 'fit, suitable.' Kṛṣṇa frames the request as conditional, leaving Nṛga the dignity of refusal. Gauḍīya pedagogy: even when teaching, never humiliate the student.

• Whose story am I dismissing without asking, even though I think I already know it?
• How does asking with reverence honor the dignity of someone who is being delivered?

Kṛṣṇa frames the question as a tactful father might: not 'what wrong did you do?' but 'what action brought you here?' — protecting the speaker's dignity even while drawing out a confession that the whole assembly needs to hear.