Randy Lenz is a minor character in David Foster Wallace's novel infinite jest. He is drawn almost as a caricature of loathsomeness, and although he is not an important character, his actions do advance the plot at one juncture.
Randy Lenz is one of many residents of a halfway house where he is supposedly trying to deal with an addiction to cocaine. However, the real reason he is there is to hide from both criminal gangs and law enforcement, since he has somehow managed to make both of them very angry. The exact offenses he committed aren't gone into in detail, but they probably involve the fact that he was selling cocaine as well as using it. In an attempt to deal with his frustrations, he secretly tortures and kills dogs and cats, actions which cause him to enrage some Quebecois, who end up shooting the novel's protagonist, Donald Gately, who is the supervisor at the halfway house. After this, he is expelled from the house, and eventually ends up being a test subject for the movie infinite jest, which probably leads to his death.
In infinite jest, Wallace attempts to portray drug addicts as real people, who even after having done terrible things under the influence of drugs, are still capable of redemption. It seems that after all this effort at portraying people even-handedly, Wallace wanted someone to describe as totally degenerate and loathsome. Lenz fits the bill: he is sleazy, amoral, pretentious, annoying and a coward who engages in sadism to make up for having no control over his surroundings. Lenz is one of the few characters in the novel who seems to have no redeeming features whatsoever. The only positive thing said about him in the book is after briefly considering lighting a hobo on fire, he is shaken by the depths of what he imagined.
An odd trend in infinite jest is that while Wallace is well aware of the bad effects of all types of drugs, he seems to reserve a special contempt for stimulant drugs, especially cocaine, and the people who become addicted to them. What the source and meaning of this prejudice is, I do not know.