Various moments could qualify as this, but arguably the most well played comes when the survivors discover the creature's feeding ground, where it's excreted the gooey, skeletal remains of its hundreds of previous victims. The camera pans over them, the faint but clear sounds of these people's horrified final screams played over the music like a ghostly echo.
Of course, that's assuming it's finished draining all of the passengers yet and some of those distant screams aren't actually happening, somewhere deep inside the monster or elsewhere on the ship. After all, we just assume there aren't any more survivors still onboard, who might have made it that long, only to run out of luck.
In addition, during the climax where a tentacle grabs Finnegan, shrieks in his face and then appears to quite vividly laugh at him, with a disturbingly human "HUR HUR HUR HUR HUR". While it might sound cheesy on paper, the dramatic directing makes it downright horrifying.
Billy's death. He falls right out of a tentacle's digestive chamber after Finnegan shoots it. Half of the guy's body is missing, but he's still alive and aware enough to feel it.
The woman who dies in the bathroom. Unbeknownst to her as she sits down on the toilet, the creature's tentacles travel up the water pipe and toward her underparts, before sinking their teeth into her buttocks and genitals and brutally savaging her crotch.
Or so we can infer. All we see is her briefly flailing and screaming before cutting to a spray of blood and a shot of her arm implicitly being sucked down the toilet. Whether this is better or worse is up to you.