Caliban's evil nature is magnified in this scene. His contempt for Prospero saturates his very being. He takes advantage of the witless Stephano by convincing him to murder Prospero. The language Caliban uses to speak of the murder is filled with violence and hatred.
However, another side to Caliban's nature is hinted at in the memorable lines he speaks at the end of the scene. He talks about the beautiful and mysterious noises of the island which soothe his soul with pleasant and healing dreams. Caliban's sensitivity to beauty displayed in this scene prepares us to accept more readily his admission of foolishness in the last scene.
In no particular order (because more than one impression is communicated at once), I get the impression of Caliban as weak-minded, as foolish, as cowardly, as servile, yet malicious and seeking power. For all that he claims he wants to be free, he seems born or designed for servitude. Lines like " How does thy honour? Let me lick thy shoe." and " I would my valiant master would destroy thee" show his willingness to cave under to authority, even that of two drunken sailors.