The goblins are just beginning to show signs of violence. Earlier in the poem they were just funny or strange; now they're starting to look "evil."
They trod and hustled her, Elbowed and jostled her, Clawed with their nails, Barking, mewing, hissing, mocking, Tore her gown and soiled her stocking (399-403)
The long list of verbs really emphasizes the violence in this scene. The goblins don't just "claw" her, they do all kinds of terrible things.
Held her hands and squeezed their fruits Against her mouth to make her eat. (406-407)
This is probably the most violent image in the poem. The goblins pin Lizzie's hands and try to force-feed her. Many critics read this as an attempted rape. Does your reading of this scene change based on whether or not this action is attempted rape?
Thought the goblins cuffed and caught her, Coaxed and fought her, Bullied and besought her, Scratched her, pinched her black as ink, Kicked and knocked her, Mauled and mocked her, Lizzie uttered not a word; (424-430)
In spite of all the violence and beating, Lizzie refuses to make a sound. By refusing to submit or cry out in pain, Lizzie turns the violence of the goblins into her own gain.
Swift fire spread through her veins, knocked at her heart, Met the fire smouldering there And overbore its lesser flame; (507-509)
Laura's recovery is described with very violent images. She experiences something like a battle between the two "fire[s]" in her body.