Lokhust Heavy Destroyer

If you activate a card's unearth ability but that card is removed from your graveyard before the ability resolves, that unearth ability will resolve and do nothing.

As Lokhust Heavy Destroyer's triggered ability resolves, first the player whose turn it is chooses a creature to sacrifice, then each other player in turn order does the same knowing the choices made before them. Then all those creatures are sacrificed simultaneously.

At the beginning of the end step, a permanent returned to the battlefield with unearth is exiled. This is a delayed triggered ability, and it can be countered by effects that counter triggered abilities. If the ability is countered, the permanent will stay on the battlefield and the delayed trigger won't trigger again. However, the replacement effect will still exile it if it eventually leaves the battlefield.