When fans refer to the DC Universe, it's often regarding DC Comics and their respective characters as a whole, but it can also be referring to the galactic universe of the DC continuity, which is a very big place, to understate it a bit.
As such, the DC Universe is filled with planets that the comics have visited a few times over the years, with some of those planets showcasing how dangerous they were to heroes like the Justice League and the Green Lanterns. So today we are going to take a closer look at some of the planets in the DC Universe to see which is the most dangerous.
10 COLU
Colu was one of the most technologically advanced planets in the whole universe and was home to a green-skinned race that gave control of the planet's government to intelligent programs that became known as Computer Tyrants after they began ruling the planet with an iron fist.
Coluan scientist Vril Dox would eventually become the computer intelligence known as Brainiac, whose city-shrinking technology would be used on Colu before Brainiac began traveling the galaxy and collecting cities. Colu has occasionally managed to fight the oppression of the Computer Tyrants (or Computo in newer continuity) but it's still a very dangerous planet.
9 GEMWORLD
Gemworld technically exists in another dimension that was created by the Lord of Chaos as a safe haven for the faeries and magical creatures that didn't want to live on Earth, but it is still a dangerous planet that the characters of the DC universe have interacted with many times, most recently in the pages of Young Justice.
Princess Amethyst is one of the main characters of Gemworld and has served on teams like Young Justice and Justice League Dark due to her experience fighting the various supernatural and magic-using threats that exist on Gemworld, which don't make it the most friendly of tourist spots.
8 RANX
Ranx was originally known as the Sentient City in its earliest appearances in the pages of Green Lantern titles due to the artificial intelligence that controlled the city, though Ranx would get a huge upgrade when it began working with the Sinestro Corps.
Ranx would increase in size to become as big as a planet and serve as the home base for the Sinestro Corps as well as one of its members, and its long-standing feud with the Green Lantern Corps (specifically Guy Gardner, understandably) would fuel its dangerous potential for years and in many different forms.
7 MOGO
Ranx's opposite number is the being known as Mogo, a sentient planet who is also a member of the Green Lantern Corps. The vegetation of Mogo often forms as a solid green band around the planet that looks like a GL ring, and the planet has a powerful connection to the Central Power Battery that powers the GLC that enables it to create powerful constructs.
Mogo has proven instrumental in various battles and has assisted in the training of various Green Lanterns over the years, while also acting as the force behind the ring's ability to find new sector guardians if the original ringbearer is killed. Mogo has proven his superiority over Ranx in battle and continues to serve alongside the GLC as planet-sized reinforcement.
6 WARWORLD
Warworld is an artificially created planet-sized battle station that was created by a conquering alien race known as the Warzoons in its first Pre-Crisis appearance, though it would later be taken over by the alien despot known as Mongul, who would use its planet-destroying weapons to build his reputation and add to his army.
Warworld is basically an overpowered weapon satellite but it has proven to be an incredibly effective battle station over the years, especially when it was combined with the remnants of a destroyed Ranx to create the ultimate Warworld, which would continue to serve as the Sinestro Corps base until it was destroyed.
5 THANAGAR
The planet of Thanagar itself isn't dangerous in the sense that Mogo and Warworld are themselves inherently dangerous, but instead, Thanagar is home to a few warrior alien races that have appeared frequently in the pages of Hawkman and related series.
The Thanagarians are a race of warriors who use the planet's unique Nth Metal to forge their weapons and technology, and whose culture has played a role in the lives of DC's Hawkman and Hawkgirl. The Thanagarians have long been at war with the Lizarkons of their own world, as well as other planets like Rann.
4 OA
OA is one of the oldest planets and previously existed in the very center of the universe as the homeworld of the Green Lantern Corps and the base for their Central Power Battery that contains the green power of will that fuels the rings of the Green Lanterns.
OA is also the home of the immensely powerful Maltusians known as the Guardians of the Universe, an immortal race of beings tasked with bringing order to the universe. OA's connection to the GLC and the power available from the Guardians and the Central Power Battery makes it one of the most dangerous planets in the DC universe when it needs to be.
3 QWARD
Much like Mogo has an opposite number in the form of Ranx, OA has an opposite as well that exists in the anti-matter universe known as Qward. The anti-matter universe opposes the regular matter universe that the majority of the DC characters reside, and Qward took its place in the center of the anti-matter universe much like OA.
Qward is home to the race of beings called the Weaponers who are known for their deadly weapons and as the ones who created the first yellow power ring worn by Sinestro. The powerful reality-threatening being known as the Anti-Monitor resides on Qward along with his creations the Thunderers, making it a deadly place to visit.
2 APOKOLIPS
The dark planet of Apokolips is covered entirely by a ruined industrial city with fiery pits that explode out of the planet's core, a stark contrast to the lush and vibrant sister planet of New Genesis that first appeared in New Gods #1 as part of Jack Kirby's Fourth World.
Apokolips is ruled by the powerful New God known as Darkseid and is largely considered by the heroes and villains of the DC Universe as one of the most dangerous and feared places in the galaxy, with even characters like Superman hesitant to make an appearance there.
1 EARTH
Of course, none of these planets have anything on Earth, home of a huge population of meta-humans with powers and abilities that could lay waste to planets on their own. While Earth would be considered to be a safe and peaceful place for those that live there, the rest of the universe might not feel the same way.
The power of the Justice League is known throughout the galaxy, while scarily powerful beings like Doctor Manhattan have altered reality on a whim, making Earth the biggest threat in the galaxy that even planets like Apokolips respect and fear, even if they don't admit it.