Bad
Bad is a concept used to describe undesirable circumstances or events.
Though bad often is used to imply moral turpitude of a person, the term more specifically refers to an unfortunate circumstance. While bad is often used as a synonym for evil, bad can also refer to something flawed or unusable. The philosopher Friedrich Nietzsche made much of a distinction he drew in German between the böse, ("evil"), which he was prepared to admire, and the schlecht ("bad"), which he disdained; in Nietzsche's thought, evil was powerful, menacing, and dangerous; bad was weak and ineffective. In African-American vernacular English, and varieties of American English that have been influenced by it, bad or badass are frequently used as compliments, an example of rhetorical irony. "Badass" can also be used to describe a person prone to physical altercations.
Amusingly for English speakers, in Germany Bad (German for "bath") is a prefix for town names signifying a spa town, as in Bad Wörishofen or Bad Kissingen.
See also: Bad (album) - a 1987 Michael Jackson album