Diabolical vs. debacle are easily confused words. The spell-check application of most word processing software programs would not catch a slip-up of these two words. Spell-check is looking for words that aren’t in its dictionary, and words that resemble words in its dictionary but are possibly spelled wrong. Spell-check isn’t perfect. It doesn’t know and can’t guess what word you wanted or what word you meant, it can only judge the words on the page. If you used words that are all spelled correctly, it gives you a pass anyway.
Autocorrect suggests words that start with the same letters. It’s suggesting what word you may want to save time, but quite often, its suggestions are pretty off base. They don’t help you out, but they do make you laugh.
Diabolical (pronounced “die-uh-boll-ick-all”) is an adjective. It describes something demonstrating or showing evil genius. [If you are familiar with Latin languages, you know diablo means devil, and that’s a source for this word.] If someone describes something as diabolical it could be evil, or it could just show unbelievable insight and genius, as if the creator were up to something.
Debacle (pronounced “dehb-ick-ull”) is a noun. It means a breaking up, a collapse, a falling apart of something.
The following story uses both words correctly:
Dulcinea thought she was a shoe-in for winning top prize at the pie contest for the tenth year in a row. Instead, it would turn out to be quite a debacle. New people had moved to town and she would need to up her game. One competitor, Debra, cooked up a pecan pie that was downright diabolical with its hot yet sweet flavors.