Orlick is a journeyman at Joe's forge (the middle step between being an apprentice and a master), and he's no good: he's a "broadshouldered loose-limbed swarthy fellow" who "slouches" everywhere (15.34). Pro tip: in a Dickens novel, being swarthy and slouching is just as much code for "bad guy" as being blond and energetic is code for "good guy." We don't need to know that this guy threatens Pip with being thrown into the furnace to know that he's a bad guy, but it helps: Orlick is mean, nasty, and kind of a creep with the ladies.
Here's a quick list of misdeeds: he threatens Pip, attacks Mrs. Joe, links up with Compeyson, plans to kill Pip in the sluice-house, comes on to Biddy, and then robs and assaults Mr. Pumblechook. Nice, dude.