Swallow-Whole-er (thumbnail)

This thing would be a swallower-whole-er. It has a hugely expansible maw with little grippy fangs all the way back down its throat, to hold on to prey it's in the process of swallowing. Clearly the gullet and abdomen would also have to be able to expand to hold anything, say, human-sized, but I see no problem with that.

It's a creeper, an ambush predator, so probably not much chop in a stand-up fight. It's the sort of thing that would sneak up on stragglers in the dark and gobble them down without, hopefully, alerting anybody too dangerous.

It has a venomous sting on the end of its tail. I guess it would probably use that to silence and immobilize its prey before beginning the swallowing-whole. I imagine swallowing something as large as an adult human would leave it somewhat torpid and sluggish of movement, so it would probably want to drag such prey to a place of safety before eating them.