If enough -1/-1 counters are put on a creature you control at the same time to make its toughness 0 or less, Host of the Hereafter’s last ability will see all of the +1/+1 counters it had when it died as well as the -1/-1 counters it had, and the same number of each of those types of counters (plus any other applicable counters) will be put onto the target creature.

If the creature that died had -1/-1 counters on it when it died, Host of the Hereafter’s ability will put those on the target creature as well. This may result in the recipient of the counters also dying.

Host of the Hereafter’s last ability puts all counters that were on the creature that died onto the target creature, not just its +1/+1 counters.

Host of the Hereafter’s last ability doesn’t cause you to move counters from the creature that died onto the target creature. Rather, you put the same number of each kind of counter the creature had when it died onto the target creature.

If Host of the Hereafter dies at the same time as one or more other creatures you control, Host of the Hereafter’s last ability triggers for each of those creatures that had counters on them, including itself if applicable.

In some unusual cases, you may end up putting the appropriate counters on more than one permanent. For example, if you control The Ozolith and Host of the Hereafter when a creature you control with counters on it dies, you’ll put the appropriate number of each kind of counter onto both The Ozolith and the target creature.