Look Back in Anger is often viewed as a drama, but it could be played as a dark comedy as well. Dark comedy mines serious subject matter for humor—generally the more taboo the better. Osbourne utilizes plenty of dark comedy throughout the play, mainly at the expense of his flawed characters. For example, Jimmy Porter is a comical figure not just because of his witticisms, but because of his flaws. Though he complains about the repetitive Sunday morning rituals of respectable people, he indulges in them himself.
A far more bleak example of dark humor in the play would be the ending. The ending is mostly tragic: Alison loses her baby and so returns to Jimmy, feeling their shared pain will allow them to better understand one another. Then, Alison and Jimmy engage in an overly saccharine love game which, depending upon how the director and actors handle it, could be a rather grotesque parody of connubial bliss. The two call one another pet names and act in ways opposite to their previous aggression towards one another, which could be presented as both disturbing and comical.
This humor is often subtle, not as apparent as slapstick or outright jokes would be. Much of the humor would depend upon how the actors choose to portray the characters as well. However, the material is layered enough to where it could be presented as a dark comedy.