I thought I was in the groove dropping answers like RATPACK, EBENEZER, and GANGSTA right in. That gave me the false impression that this puzzle was going to be straightforward, instead, in the end, it took me for a SCRAPE round to Dinsdale's place. Things really blew up in the northwest with KABLOOEY (Bad way to go) crossing ABUDHABI and OLGA, amid other uncertainties. I only just now understood 4D. "Giant competitor" (PADRE) on reviewing the clues.
I spelled GROMeT wrong, leaving me with LEA_eN for "Show immediately preceding another," a clue I had trouble parsing. Other NEMESES included NBAJAM, ASWAN, ADOANNIE, and NOSLOUCH.
Happily, I am not familiar with the term NIGHTMAREFUEL, but I was able to guess the nightmare part pretty quickly. EXOTICA and XRATED really SOUPED up the mid section. I liked LUKEWARM and TASTEBUD, too.
GROAN for "Express stress, in a way" I thought was way off base. Not unpossible, of course, just SEWNON interesting, nor apt.