The Joker had been a relatively benign "goon" for a long time in the Batman comics from the 1950s onward. The Jerry Robinson characterization of the character as an unsympathetically sick and dangerous psychopath (as in the noir-like 1940s issues of Batman) had come back in the 1970s.
Though a somewhat cheerier attitude would come back to Brave and the Bold by the late 1970s, for a brief time an urban-corruption and cultural malaise hit the Batman scripts of DC Comics.

Batman 291 cover with Catwoman
Brave and the Bold 105 - Batman and Wonder Woman
Brave and the Bold 107 - Black and White Page
Brave and the Bold 109 Cover - Batman and the Demon
Brave and the Bold 111 Cover - Batman and the Joker
Brave and the Bold 111 splash page
Brave and the Bold 111 Page 14 - Joker and the Gates of Fear
Brave and the Bold Manbat - Issue 117 - Cover - Batman and Manbat
Brave and the Bold Manbat - Issue 117 - Page 5
Brave and the Bold Manbat - Issue 117 - page 6
Brave and the Bold Manbat - Issue 117 - page 17 - Manbat
Brave and the Bold 178 - Batman and the Creeper
Brave and the Bold 160 - Supergirl
Detective Comics 444 - Cover - Bat-Murderer
The Spectre from Adventure Comics 431
The Spectre from Adventure Comics 431 - The Valley of Death
New Jim Aparo collection coming from DC Comics. Hope it includes the run of Archie Goodwin-penned tales form the mid-seventies. Cover of the book (as advertised so far) is a recoloring of the art Aparo did for the cover of Brave and the Bold 111. See it at 1400 pixels here.