Which word best describes a long, angry speech that is usually very critical?

The term "tirade" is the most suitable choice when describing a long, angry speech that tends to be highly critical. A tirade typically signifies a lengthy and passionate outburst, often directed against a particular group, person, or issue. It conveys a sense of vehement disapproval and is characterized by emotional intensity.

While "rant" also pertains to a similar idea, it can be more generalized and may not always carry the same weight of formal criticism as "tirade." "Diatribe" can also depict a bitter criticism similar to "tirade," but it's often used in contexts that emphasize abusive or harsh language, lending it a slightly different connotation. "Sermon," on the other hand, is generally associated with a moral or religious discourse, focusing on teaching or instruction rather than a critical and angry diatribe. Thus, "tirade" specifically captures the essence of a long, angry, critical speech in the context provided.