apuntillar

A bullfighting term for the final thrust with the puntilla (a short dagger) that dispatches the bull after the matador's main sword thrust — by extension, used figuratively for finishing off something already defeated or doomed, like a failing business or a lost cause.

• El puntillero apuntilló al toro tras la faena. — The bullring assistant finished off the bull after the performance.
• La nueva ley apuntilló al negocio, que ya estaba en crisis. — The new law finished off the business, which was already in crisis.
• Ese gol apuntilló las esperanzas del equipo rival. — That goal finished off the rival team's hopes.

Using apuntillar for any kind of ending — it specifically carries the sense of delivering the final blow to something already weakened or dying, not just concluding something neutrally; terminar or acabar are the general-purpose words for that.