If I had Ugin's Conjurant with 10 +1/+1 counters on it (and no other effects modifying its toughness,) and my opponent cast a Banefire for 5 damage on it, would +1/+1 counters get removed from the Conjurant, as well as the damage being dealt, killing the Conjurant?
Relevant text on Banefire:
Banefire deals X damage to any target. If X is 5 or more, this spell can't be countered and the damage can't be prevented.
and on Ugin's Conjurant:
If damage would be dealt to Ugin's Conjurant while it has a +1/+1 counter on it, prevent that damage and remove that many +1/+1 counters from Ugin's Conjurant.