• nirbhinna-kumbhāḥ — whose forehead-protuberances were split
  Compound: nir + bhinna (split open) + kumbha (the elephant's frontal lobe, traditionally said to contain pearls). The pearls are crushed by arrow-tips. Image of opulence destroyed — exterior glory does not protect when standing against Bhagavān.
• kandharāḥ — whose necks (were severed)
  Plural of kandhara (neck). Same word repeats later in the verse for the shoulders of foot-soldiers. The dismemberment is total — no rank of army (elephants, cavalry, chariots, infantry) is spared.
• padāyataḥ — foot soldiers
  Synonym of pādātika. The verse names the four classes of akṣauhiṇī (gaja, aśva, ratha, pādātika) and slays each in turn — the formal completeness of the destruction parallels the formal completeness of the army's structure.

• What 'pieces' of an opposing inner army have you imagined surviving when scripture says they don't?
• Where could fuller surrender to Kṛṣṇa's action ensure complete dismantling?

Elephants with split foreheads, horses with severed necks, chariots without horses or masters — the battlefield turns into a single anatomy lesson on the brittleness of all that does not take shelter of Kṛṣṇa. Even gigantic akṣauhiṇīs are finally only meat without Him.