Contrary to the subversive popular belief, size does matter, at least when it comes to physical confrontations. The statement holds true for comic books as well particularly in DC universe; some of the most menacing supervillains in DC would never have gotten their notoriety if they were only half their size.
Besides, it's a proven fiction tactic to make the villain bigger than the heroes ever since that parable about David and Goliath spread like wildfire. People love underdogs, after all. Hence, DC has its own share of giants when it comes to supervillains. Due to their size, even Superman alone wouldn't be able to beat most of them. Here are 10 of those absolute units.
Hailing from another planet is the tyrannical ruler of Warworld, Mongul. He has always been a massive thorn on the Justice League's side with how violent and warlike he is. Mongul stands at an imposing 8' or eight feet tall, weighs 1125 lbs. and can easily go toe-to-toe with any Kryptonian. He has even proven to be more skilled than them in terms of combat.
In that regard, he's one of the few foes Superman wouldn't want facing often or again. He has even shown that he is capable of defeating Superman in combat and for that matter, any other member of the Justice League. Still, he's actually the smallest dude in this list...
Next up in the waiting line arranged by height is another supervillain capable of giving Superman some nasty nightmares: Darkseid. Everyone in DC is sure to know this evil guy. Like Mongul, Darkseid rules over his own dark domain in the corner of the universe called Apokolips. He was so imposing and successful at what he does, Darkseid even inspired Marvel to create their own dark-skinned alien conqueror but with a purple complexion instead.
Anyway, Darkseid or at least his physical avatar stands at a vast 8'9" and weighs as much as 1815 lbs. He's a lot stronger than Mongul and can easily erase beings with his Omega Beams without even touching them. Despite his godly powers, he still sometimes goes into fisticuffs though believes that kind of fighting is beneath him.
Throughout many issues of DC comic books, Doomsday's size and appearance kept changing. At his biggest version, however, the certified Kryptonian-killer has stood at a monstrous 8'10" and weighed more than 900 lbs. Despite his size, he's a seemingly mindless monster whose only instinct is to kill and destroy.
Even so, Doomsday has proven to be capable of defeating the likes of Darkseid (unceremoniously, though). For that matter, Doomsday has no problems obliterating the likes of Superman. He does have another and an even bigger version such, like the one shown in Batman v Superman: Dawn of Justice.
Sadly, the villainess Giganta is the only female in this list but even so, she's quite impressive in the height department. Normally, Giganta would be at a normal human height for someone her age, but when she grows, she can go as high as 25 stories tall or approximately 270 feet, perhaps even higher. It would then be safe to assume that she weighs 700 tons give or take.
This essentially makes Giganta a lot bigger than the more dangerous mini-titans like Doomsday or Darkseid. She isn't necessarily more powerful than them, however, and it certainly wouldn't take a Superman or even a Wonder Woman to defeat her.
Even more obscure a villain than Giganta is the Adjudicator. Some of you might not have heard of him since he technically got erased after the multiverse collapse of Crisis on Infinite Earths which ran from 1985-86. Nevertheless, the Adjudicator is one of the literal biggest villains to threaten Earth.
His actual size is never confirmed but he has been shown to be taller than the Washington monument. The monument stands at 555 feet, meaning the Adjudicator is somewhere around that size. Additionally, the Adjudicator's origins and the alien race where he belongs was never specified, only that it was old and powerful. His hobbies include playing with worlds he didn't care for, much to the chagrin of the Justice League.
At this point, the height, weight, and general size of the supervillains are just pure speculation. However, they are no doubt huge, based on their description and portrayal alone. Trigon, the resident super-demon of DC is no exception. Ever since he was born, he set out to do horrible things; as a baby, Trigon slaughtered his own mother and the very cult who was responsible for his creation.
By the time he was six, he had already conquered his own planet. For that matter, Trigon is doubtlessly powerful and has the size to precede his reputation. At times he is drawn in a way that makes normal-sized superheroes look like mini-figurines. His size seems to vary depending on every appearance, though.
Anti-Monitor DC's closest supervillain ever to Marvel's Galactus in terms of motivations and likeness. As you can imagine, Anti-Monitor is also a vast and physically striking being. His size does vary in a similar frequency to Trigon but generally makes regular superheroes look like they're his action figures.
Then again, Anti-Monitor is often considered as a universe destroyer. That means it's safe to assume he can change his size depending on his needs at the moment; for all we know, he could even become as big as a universe itself in order to destroy one.
3 IMPERIEX PRIME
Imperiex Prime is similar to Anti-Monitor or Galactus; he's also a huge universe destroyer being who can reduce the likes of Doomsday to mere atoms with a blast. Oh, and he's also the embodiment of entropy in the DC universe, meaning he has a free pass to destroy anything and everything. As such, he's absolutely massive.
Imperiex isn't exactly a solid being but actually a form of pure energy which is contained inside a suit of armor. In this physical form, Imperiex Prime is described only as colossal though "galactic" should be a more accurate term since we can see Imperiex sometimes bigger than planets.
2 THE GREAT EVIL BEAST
There are many names for The Great Evil Beast in DC but all of them are synonymously ominous and sinister: Original Darkness, the Evil, Shadow, etc. It's more of a conscious abstract being whose chosen physical form resembles a black swirling void which sometimes appears as a swelling wave that's out to consume everything.
In that regard, there is no means of measuring The Great Evil Beast. After all, you can't really measure darkness, can you? When it comes to powers, not many can stand in its way. The Great Evil Beast even defeated the formidable Spectre who purposely increased his size to colossal proportions for the fight.
1 DAX NOVU/MANDRAKK
Dax Novu belongs in the same race as the Anti-Monitor, which is the Monitor race. They're pretty much the watchers/feeders of the multiverse and have unimaginable omnipotence. Dax Novu took on the name Mandrakk. He was then imprisoned by his fellow monitors after revealing to them that they were destroying the multiverse.
Dax Novu, at his mightiest form, holds the combined power of 52 universes; this makes him bigger than the multiverse. He does tend to manifest in smaller forms when fighting superheroes, though. Regardless, he has defeated both Spectre and The Radiant, making him the ultimate threat of the DC universe and is even so powerful, he knows of the fourth wall.