• ajite — against the unconquerable one (Kṛṣṇa)
  Locative of ajita. Sanskrit poetry loves the irony of an attack 'against the unconquerable' — the case-ending names the futility before the verb arrives.
• śastra - kūṭam — mountain of weapons
  Kūṭa = peak, heap. The asuras' onslaught is described as terrain — a mountain — that the Lord must pulverize to expose them.
• amogha - vīryaḥ — whose prowess is never frustrated
  Amogha = 'not in vain'. A key Vaiṣṇava epithet — when applied to grace (amogha-dāyī) and when applied to power (amogha-vīrya), it names what Bhagavān cannot fail to do.
• tilaśaḥ — into particles the size of sesame seeds
  From tila (sesame seed). A unit of fineness in Sanskrit — 'sesame-sized' is the standard idiom for 'utterly pulverized'. The verse's most concrete image.
• mārgaṇaiḥ — with arrows
  From √mārga (to seek, track). Arrows are 'seekers' — they find their target. The lexical hint: the Lord's weapons are intentioned, not blind.

• Where do you face multi-weapon attack from a single direction?
• How does the Lord's single sustained response handle multiplicity?

A mountain of swords pours toward Kṛṣṇa and He cuts each blade into sesame-sized fragments — like a thresher pulverizing chaff. Whatever rises against Bhagavān is reduced to the smallest unit of itself; the asuras' fury, multiplied, becomes only finer dust.