The definition of a "big bad" can vary depending on the context, but for this discussion, it refers to the powerful, world-ending, cosmic conqueror-level villains. So, a lot of DC's most compelling and most popular villains tend to be the street-level guys or characters, who, if thrust into a world-conqueror role, would seem out of place: Joker, Bane, Two-Face, Catwoman, Harley Quinn, Deathstroke, Captain Cold, etc. And don't get me wrong, that is not a bad thing. In fact, one of the things that makes those guys compelling is their down-to-Earth quality. However, I was just wondering why not many of DC's most mentioned villains are their world-ending cosmic tyrants.
The exceptions to that are Sinestro, Lex Luthor (sometimes), Brainiac, Black Adam, the Anti-Monitor, and of course, Darkseid. However, even of the ones I just mentioned, there are caveats.
And it's not like DC doesn't have more of those types of villains. They do. But DC seemingly benches a lot of them in favor of other characters from more popular franchises. When was the last time Mongul was a universe-wide threat? We last saw Krona as a big threat was back in like 2011 (almost a full decade ago) during the War of the Green Lanterns arc IIRC. Ra's al Ghul I think is used effectively as is and is one of DC's best villains, but I wouldn't call him a cosmic threat. Vandal Savage has the potential to rise to the level of a cosmic-conqueror type and, if anything, I think the Young Justice animated series uses him to his full potential, but he's not so used in the comics. General Zod can be such a villain but he's rarely seen outside of Superman books. Doomsday is not a conqueror but a rampaging monster. Trigon could absolutely be that level of a villain, but he hasn't been taken seriously as a threat since the Wolfman/Perez NTT run and every subsequent appearance of his seems to try and rehash that arc. I don't know if Ares despite being a literal god has ever even appeared outside of a Wonder Woman comic.
Like, why isn't Lex going to war against Ares or Vandal Savage in the current Year of the Villain arc instead of just another Batman character?