It has been 30 years since the DC Animated Universe began with Batman: The Animated Series which continued up to Justice League Unlimited with the occasional animated film such as Justice League VS The Fatal Five. In those 30 years, Kevin Conroy remained the definitive voice of Batman.
With Kevin Conroy's tragic ing, fans are returning to the shows to witness the encounters with the many villains he faced across the different shows. While many are iconic, others were more than just cases; they were rivals that pushed Batman in more ways than one and proved to be the most dangerous threats he faced.
10 Two-Face
Harvey Dent is a threat to Batman in multiple ways as the DC crime lord known as Two-Face. As Gotham's former district attorney, his extensive knowledge of the city, as well as his high connections, allow him to recruit the best criminals into his army. If he is able to get the numbers, he can prove to be a physical threat to Batman.
Due to the fact that Two-Face had also been a close friend of Bruce Wayne's, there have been occasions where the criminal mastermind has been able to get the upper hand on Batman because of Bruce's struggle to fight his friend. Unfortunately, this isn't enough to take "the world's greatest detective" down since he has proven, more than once, that he is skilled enough to take on groups of criminals and has quickly begun to click on to Harvey's plans.
9 Scarecrow
Every time the Scarecrow appeared, fans knew he would be a danger to Gotham as he always managed to get under everyone's skin - particularly when equipped with his Fear Toxin. When Batman is first exposed to the Fear Toxin, it led him down a path of fighting his own inner demons as the gas brought his worst fears and insecurities to life (e.g. blaming himself for his parents' death). The iconic villain also managed to get the upper-hand once again in The New Batman Adventures when he took away Batman's fears and inhibitions, turning The Dark Knight into a ruthless killer, who even tried to attack Tim Drake.
Fortunately, the Scarecrow doesn't exactly worry Batman since the toxin is ineffective once his victims conquer their fears or have access to Batman's antidote. The villain has also proven to be his own enemy since his hubris and ego has led him to make many mistakes (such as Batman and Robin using his own toxin against him).
8 Mr. Freeze
Although Batman knows that Victor Fries is capable of good, this hasn't stopped a rivalry between them. Initially, Mr. Freeze was a kind man and husband - however, this all changed when he became consumed by corporate greed and revenge.
In the multiple times that Batman and Freeze faced off, Freeze proved to be a deadly villain thanks to his high-tech suit that gave him super strength combined with his cryo-gun that could encase nearly anything in ice. Each time, Freeze was upgraded to the point where he was hardly even human and even deadlier. Thankfully, Victor is more human than most villains and so Batman can often reason with him despite his capabilities.
7 Ra's Al Ghul
With unlimited resources and control over the League Of Assassins, Ra's Al Ghul is a fanatic who seeks to raze major cities, such as Gotham, to the ground and rebuild them in what he sees as a better image. Combined with his immortality (as a result of the Lazarus Pits), Ra's is arguably the most dangerous terrorist in history.
Batman is always there to be his nemesis, and it's never an easy fight for everybody's favorite Dark Knight. Even in the years of Batman Beyond, Ra's was willing to possess the body of his own daughter to manipulate Bruce mentally and emotionally. However, even though Batman was pushed to his limit to defeat both Ra's and Talia, he still managed to come out on top thanks to his intelligence and quick thinking.
6 Lex Luthor
Although he is more of a Superman villain, the DCAU portrayal of Lex Luthor would end up becoming a villain for the entire Justice League. Lex Luthor is essentially the anti-Bruce Wayne; they were both handed their riches and resources, but Lex only used them to ensure power for himself.
He may not be the evilest villain in the DC universe, but he is always a problem for the Justice League and Batman (especially when he became fused with Brainiac). It's certainly one of the first times that Bruce has struggled against an opponent since they have been fairly matched, but he has won a fair amount of battles due to his connections and alliances.
5 The Phantasm
Appearing in one Batman: Mask Of The Phantasm, The Phantasm was, essentially, a darker version of The Dark Knight, who took out Gotham's criminals by murdering them in cold blood. She also became famous because of the reveal of Andrea Beaumont as her true identity.
Batman became torn because of his love for Andrea as well as his compulsion to bring down criminals. Andrea ends up being one of Batman's deadliest threats since she refuses to give up her revenge resulting in Batman in one of his most damaged states by the end of the movie.
4 Justice Lord Batman
Batman is already a man who can take down an entire Justice League thanks to his contingencies so an evil dictator version of Batman is pure nightmare fuel.
When the two variants of Batman fight, they are evenly matched when it comes to skills, tactics, and arsenal. So, it becomes a battle of wits, and the real Batman is forced to use what he knows about himself to fight this evil Batman with words.
3 Amanda Waller
Batman and Amanda have so many similarities; they both are overly prepared for any situation but also fight for a better tomorrow. However, the DCAU's Amanda "The Wall" Waller fights only for herself and what she views as a better tomorrow which is basically just her above everyone else.
Batman, on the other hand, has a more altruistic goal, fighting to protect others and providing a future where everyone is safe. Batman is also far more trusting of his team, despite his contingencies. So, these two tend to clash every time they meet, even to the point where Waller threatens Bruce Wayne and his secret.
2 The Joker
Despite having no powers, little to no funds, and a secret origin, the Joker manages to do more against Batman than most powerful supervillains are able to. Mark Hamill's portrayal of the Joker pushed what was allowed on television (because, for every jovial plot, there was also an act so sinister and vile that it rivaled some of the most twisted villains in horror movies).
The prime example is in the DCAU's Joker ultimate send-off in Batman Beyond: Return Of The Joker, where he tortured Tim Drake and transformed him into another Joker. He then used Tim like a vessel to cause more chaos in the cyberpunk future of Gotham City. Whenever Joker comes out of the shadows, Batman is aware that death, destruction, and despair will follow.
1 Darkseid
When it comes to threats, it isn't easy to top Darkseid. He's the big villain of the DC universe that even at its strongest, the Justice League still struggles to fight and that is shown in both Justice League and Justice League Unlimited. While the Joker is a more personal villain, Darkseid is easily the most powerful villain Batman faced in the DCAU.
With his seemingly unlimited armies, Omega Beams, and strength that rivals Superman with none of the weaknesses, Darkseid nearly destroyed and conquered Earth multiple times. The Justice League had to pull together and use all of their skills, including Batman's tactical analysis, to barely gain a victory.