OK, so they didn't actually kill the creature, but they got through the encounter alive.
In one of the WotC modules there is a roper who is waaaay above the party's level (the point of the encounter is to teach the party that there are some fights they cannot win). So this roper, standing across a very cold stream, has the entire party, except the fighter, weakened and being dunked in this stream, taking hypothermia damage. The fighter nailed the roper with some alchemist's fire, then negotiated for the release of his comrades.
The resolution was that the fighter went outside the dungeon, grabbed one of the party's donkeys, and brought it down as an offering of fresh warm-blooded food for the lonely roper. "MMM...donkey! I haven't had donkey in years!" is still a popular catchphrase with the group.
In one of the WotC modules there is a roper who is waaaay above the party's level (the point of the encounter is to teach the party that there are some fights they cannot win). So this roper, standing across a very cold stream, has the entire party, except the fighter, weakened and being dunked in this stream, taking hypothermia damage. The fighter nailed the roper with some alchemist's fire, then negotiated for the release of his comrades.
The resolution was that the fighter went outside the dungeon, grabbed one of the party's donkeys, and brought it down as an offering of fresh warm-blooded food for the lonely roper. "MMM...donkey! I haven't had donkey in years!" is still a popular catchphrase with the group.