What's the Work?
Ultraman Leo is the seventh series of Ultraman franchise and probably the darkest and most violent entry in Showa Ultra continuty. The story begins with Ultraman Leo, from the destroyed planet L77 of the Leo constellation, joined MAC team in his human form of Gen Ohtori following a battle against his arch-enemy, Alien Magma and his minions, Giras Brothers, and was trained under Dan Moroboshi/Ultraseven, who was heavily injured following the fight against Alien Magma.
Who is He/What Has he Done
Commander Black, also known as the Black Directive, is the main antagonist in the final arc of Ultraman Leo. He was only introduced in Episode 40 after a long time of lacking major villains since Alien Magma perished.
(People actually said that his introduction, well, is actually a Diabolus ex Machina made by Tsuburaya Productions to kill off characters, as the viewers of Leo made an immense flop that the producers had to kill off characters to save the budget, and it wasn't enough to save the series, since its main works went into a hiatus before the launch of Ultraman '80, then another hiatus hit...)Anyway, let's talk about this guy. Commander Black is the leader of Black Star and its biological weapons known as Organic Saucers/Saucer Beasts. In Episode 40, he came to Earth with his first Saucer Beast, known as Silver Bloome, to make it attack the Space Station of the Monster Attack Crew, killing most of its members except Dan and Gen, and swallowed the entire Space Station. After eradicating MAC, Commander Black went into the city and summoned Silver Bloome to kill citizens and rampaged inside the city, killing many victims (children included) and caused the deaths of Takeshi Nomura, Momoko Yamaguchi and Kaoru Umeda, while Commander Black laughing madly at the mayhem until Leo destroyed the monster.
That was only the start of several attacks followed by his other Saucer Beasts, most notably Satan Mora, that lauched its aerial attack all across the city only to find Gen; and Nova, which brainwashed a child and spreaded toxic fume to make people gone insane, attacking each other in the process. Black Commander seems to have a taste over brutal kills since all of his monsters induced brutal and destructive attack (like Nova's insanity gas and Silver Bloome's caustic acid), and trying to break Gen/Leo's spirit either through brainwashing citizens into attacking him or with notions of harming children that bonded with Leo so that he would get him.The most horrendous example of his heinous actions is shown in Episode 50, where he captured Leo with the help of Alien Bunyo, a humanoid Saucer Beast mercenary, having Leo trapped in his Ultraman form and shrunk down to human size, so that Commander Black could personally launch his torture on him. He managed to kill Leo through mutilating him with a JIGSAW, while laughing insanely as Leo was cut into pieces. Commander Black then sent Alien Bunto to reveal his monster form and went into a rampage, and if it wasn't Ultra King who resurrected Leo, humanity will be destroyed for real.
Then, it came the final episode, where Commander Black sent his final monster, Black End, to attack Leo while holding the hero's young friend Toru hostage, so that Leo would be hestitated and got attacked by the monster. When the children that became Gen's pupil attack him to save Leo, Commander Black summoned the Black Star and tried to make it crash into Earth out of pure spite. Fortunately, Leo destroyed Black End and the Black Star via crushing Commander Black's crystal ball, as the vile alien finally perished in vain.
Well, simply put... we cannot expect PE villains from a Japanese Tokuatsu in 1970s to have their mitigating factor. He enjoys the chaos brought by his action and shows nothing else.
Ultraman Leo is a dark and violent series, but the story is actually loose. Most of the aliens and monsters before the Saucer Beasts were actually generic Showa Ultra villains (save for a few exceptions like Alien Babarue).
There was a major villain, Alien Magma, who did serve as Leo's archenemy and arguably the first half's main villain, but his apperance was limited into just two episodes. None of the villainous kaijus aside from Giras Brothers were related to him. In addition, Alien Magma's genocide and total destruction bestowed upon Planet L77 was never shown on-screen, so the brutality was not specific (as mass destruction is a normal thing for a Ultra villain) and thus he cannot be count.
Nevertheless, Commander Black became the first major antagonist in Ultraman Leo that tied up the plot since Alien Magma, and exceded him because of how direct, gruesome and explicit his actions caused. He had more on-screen vile actions and was much more revelant to the overall final arc, not only trying to break Leo's body, but also trying to break his spirit and faith, gleefully through harming the humanity he tried to protect.