Following the success of the animated Justice League series, a sequel series was announced called Justice League Unlimited that aimed to increase the size of the team and focus on new heroes and members that the first series didn't allow. The series ran for three seasons and introduced over thirty new members to the team.
This meant that while the core team of heroes like Superman and Batman still appeared, they were often split up with new members on different squads.
In order to keep things interesting, we are going to ignore the incredibly strong core team members from the first series and some heroes who only had a cameo to explore the most powerful new members of Justice League Unlimited.
10 BOOSTER GOLD
Michael Jon Carter grey up in the 25th century, and one night while working as a night watchmen he stole a security bot named Skeets and a number of display items that included a Legion flight ring, a force field belt, and a power suit, that provided enhanced strength and durability, flight, the ability to generate force fields and energy blasts.
Booster Gold appeared in a number of team fight scenes and missions, he really displayed both his heroism and dedication to the team in "The Greatest Story Never Told." While Booster is working crowd control for the League, he manages to save the world from a separate catastrophe, although he receives none of the credit.
Zatanna had a long history in the DC Animated Universe before she joined the team in Justice League Unlimited, and during that time she went from powerless stage magician to talented sorceress. However, the animated version of the character never really reached the same potential as her comic book counterpart.
A good example of this is in "This Little Piggy," when the League comes to Zatanna for guidance in a magical matter. While she was definitely helpful in the case, her magical ability still wasn't powerful enough to undo Circe's curse that turned Wonder Woman into a pig.
With such a large cast of characters, JLU wasn't always able to give all their team members the proper attention they deserved. Albert Rothstein was the Atom-Smasher, and while he has a very interesting backstory involving multi-generational legacy heroes, he was primarily used in battle scenes that required some extra muscle.
As one of the team's main powerhouses, Atom-Smasher was able to increase his size and density, which gave him enhanced strength on top of his already increased stature. Atom-Smasher was a great example of the kinds of characters that were seen in the series, as he wasn't the most well known DC hero.
7 BLACK CANARY
Dinah Lance featured in a number of episodes and soon became a leader among the new members of the Justice League, as well as the romantic interest of reluctant member Green Arrow. Dinah Lance is not only one of the DC universe's most skilled fighters, but she also has a powerful sonic scream she calls the Canary Cry.
While there may be some Leaguers with more potential power than Black Canary, she more than earned her place among the elite of the team in episodes like "Grudge Match," when she takes out other mind-controlled female Leaguers in an underground fighting ring.
6 RED TORNADO
The android known as Red Tornado was created by the mad scientist T.O. Morrow who became a superhero and joined the Justice League when they opened their ranks to new members. Red Tornado was often seen working alongside the other heroes against the larger threats, though he did feature prominently when another android creation appeared (more on him soon).
As an android, Red Tornado has a body that provides enhanced strength and extreme durability, though he was destroyed and rebuilt over the course of the series. He also has the ability to manipulate wind and generate high-velocity cyclones, whirlwinds, and tornadoes.
Superman was a large part of the first Justice League series, but he took a back seat to some of the other members in JLU. That doesn't mean his presence wasn't felt, as the League inducted a few new members from the Superman family, including John Henry Irons/ Steel.
Steel first appeared in Superman: The Animated Series before joining the team, but he played a major role in a number of episodes as one of the team's main tech minds. His power suit was built to replicate the powers of Superman and gave Irons enhanced strength, durability, flight and his hammer was also able to fire energy blasts.
4 CAPTAIN ATOM
Captain Atom was a former Army captain who volunteered for a military experiment that turned him into living nuclear energy that required a containment suit. Atom didn't initially work well with his League teammates due to his rigid military personality, but he soon proved himself to be a valuable asset to the team.
Captain Atom is able to fly and has enhanced strength, but his greatest power comes from his ability to absorb and manipulate energy. Given the makeup of Captain Atom's body, if his containment suit is ruptured, he will reach critical mass and explode; however, he can reform himself in a new containment suit.
Supergirl was another character who first appeared in Superman: The Animated Series, and she was based on Kara Zor-El from the comics, though at the time she had been erased from the continuity. Kara In-Ze was created for the series and given new costume, which proved popular enough to earn an appearance in the comics as well.
Supergirl was one of the main characters of the show and had the same powers as Superman. A clone of Supergirl named Galatea would factor into a number of episodes and demonstrate the animated Supergirl's powerful potential, though Supergirl would manage to eke out a win.
2 DOCTOR FATE
In the comics, Doctor Fate is one of the most powerful magic-users in the DC Universe, and while he didn't always display the same levels of power on the animated series, he was still one of the most powerful magical characters represented on the show.
Kent Nelson wears the Helmet of Nabu, which along with his mystical amulet and cloak grant access to incredible magical energy. His own knowledge as an occultist was only enhanced once had access to the libraries in the Tower of Fate, which also served host to a few members of the Justice League over the course of the series.
We might be stretching the term "member" a bit here, but bear with us. As we previously mentioned, Red Tornado wasn't the only sentient android who appeared on JLU, and while A.M.A.Z.O. may have started out as a villain, he was shown to be working alongside Doctor Fate, Aquaman, and Hawkgirl on a Justice League mission.
Amazo was created with nanotech that allowed him to copy the powers and abilities of other heroes, including the entire roster of the Justice League. His continued absorption of abilities and growing sentience evolved Amazo into one of the most powerful characters in the DC Animated Universe, capable of moving entire planets into other dimensions on a whim.