Audience-Alienating Premise: The show is a Deconstruction of most Toku tropes, back before deconstruction became widespread in Japanese media. This show was so much Darker and Edgier than expected that it may have led to the lowest ratings so far in the franchise (single digits). Also, Gen's Training from Hell got old quick. It may also account for the slight Retool after Episode 13, when Leo began using more energy-based attacks, as opposed to his Bare-Fisted Monk exploits early on. Ultraman Leo would have fell into Too Bleak, Stopped Caring territory if not retooled. Despite not being very popular in its first run, audience opinions of the series have generally improved since then.
Awesome Music: Both theme songs, Gen's training music from Ep. 7 (involves his True Companions throwing boomerangs at him), and the Theme Music Power-Up from Ep. 1 as Leo swooped down to save Seven (reprised in Ep. 22, during Astra's first scene).
Base-Breaking Character: Dan. Is he a stern teacher that's just frustrated with Gen's hotheadedness and only wants to help him become a true hero, or is he an abusive bully who torments Gen for things that are out of his control?
Another side of this is that Dan may be more frustrated with his current situation: He's powerless to stop possibly one of the most aggressive waves of kaiju ever, his men are constantly outgunned and being killed off left and right, and the only thing he has for backup is a hot-headed rookie. Of course he's going to project this on Gen as (sometimes) unreasonable expectations.
He may very well be suffering from PTSD. Back in the original show, his constant and escalating battles took a toll on his body, forcing him to go home. That, his subsequent adventures (on- and off-screen), plus his painful (and no doubt humiliating) defeat in Episode 1, had to hurt his spirit as well. He's a bit of a Death Seeker here, knowingly using his Ultra Psychokinesis until his face literally turns blue. You can tell his methods are pretty desperate at times. Also, others now look up to him, especially Leo. Dan's cross is not easy to bear.
Big-Lipped Alligator Moment: Episode 12, which told a story of a brave but reckless man who joined MAC off the street, had only three characters if you count the kaijuu (MAC and the rest of the cast show up at the end), and ended with the man leaving MAC for parts unknown. It was all the more startling because it was Played for Laughs.
Episode 29 came out of the blue, has nothing to do with future episodes, and it brought no closure for Dan. It was just a case of Mistaken Identity.
Bizarro Episode: "The Leo Brothers vs the Space Demon Alien", which features Alien Akumania, is just... weird. The monster itself doesn't look too scary by the series' standards, but it has the ability to create illusions and hallucinations, trapping the main cast in an apartment and using it's powers to taunt them. Said episode is filled with trippy visuals and epileptic camera work, from hands mysteriously coming out of walls and floors, to poltergeist activity like a phone coming to life and a mysterious green mist that comes out from a closet trying to swallow everyone. And then the alien reveals itself to fight Leo, by trapping Leo in a dark void for most of the battle. And somehow, it's NOT one of Akio Jissoji's contributions!
Broken Base: Depending on who you ask, Leo is one of the best Ultra series or one of the worst. The former side adores its Darker and Edgier tone (especially given the extremely childish Ultraman Taro that preceded it) and daring writing that went to new directions for the franchise, the latter side cannot abide the series' portrayal of Dan Moroboshi (especially since Ultraseven is considered one of the greatest Ultra series) and its wasted ideas, such as the usage of Astra.
Catharsis Factor: Commander Black getting an undignified death at the hands of a group of kids.
Complete Monster: Commander Black is a psychopathic alien invader from the Black Star. Arriving on Earth, Black makes his presence known by having Silver Bloome eat MAT and an entire shopping mall full of people alive in a rampage, killing hundreds. During his invasion, Black would make a habit of directing his monsters to directly attack and kill people in horrific and sadistic ways, as well as targeting children who had befriended Leo in order to get at him. He would also mass brainwash the citizens to attack Leo. After managing to capture Leo with the assistance of Alien Bunyo, Black would have the hero beaten, frozen, and then personally hack him into pieces with a saw while he was still conscious. During the fight with his final monster Black End, Black would take Leo's young friend Toru hostage at sword point to force the hero to allow himself to be brutally beaten by the monster. In one last act of spite, as he's beaten to death by the very children he used to try and get at his nemesis, Black summons the Black Star to crash into Earth. An utterly depraved alien conqueror, Black remains one of the most vile characters in the history of the franchise.
That MAC team member from Episode 12, the one who looked like a homeless man. He was very lucky...
Silver Bloome is very memorable for being the one to annihilate MAC and kill off most of the main cast, despite only appearing in one episode within the entire franchise.
Nova is well-loved for the sheer contrast between its simple, almost comical appearance and the horrifyingabilities it possesses. Its sheer popularity has earned it multiple reappearances as one of the Breakout Villains of the series.
Fan Nickname: Nova is sometimes called "Blanket Man", both affectionately and derogatorily, due to the simplicity of its design making it look like the suit actor was simply draped in a red blanket.
Fanon: While the show itself stated that an individual Alien Magma with its twin kaiju were solely responsible for the destruction of Leo's homeworld, fans and other writers found it more logical that an army of them were responsible for its destruction. Decades later, Ultraman Regulos made this canon.
Heartwarming in Hindsight: Episode 29 has a Human Alien bearing a likeness to Anne who is the adoptive mother of the psychic alien Uringa and Dan himself stop the young alien with his own psychokinesis. In Heisei Ultraseven, Anne is married and has a son named after Dan.
Hilarious in Hindsight: A powerful organization's huge offshore operating base is almost completely annihilated from a surprise attack lead by a mysterious man dressed in black clothing, most prominently a wide-brimmed hat and a black longcoat. Sound familiar?
I Knew It!: A popular theory among fans and writers from behind the scene alike has it that Leo's homeworld Planet L77 was destroyed by an army of Alien Magma instead of a singular member and his pair of Giras monsters per what the series suggests. The Ultraman Regulos miniseries would confirm that it is the case, which also introduces some higher-ranking members of the Magma race in the frontline of the invasion force.
It Was His Sled: Most people watching the show for the first time know that Seven is disabled and MAC is annihilated.
Like You Would Really Do It: Audiences watching episode 40 would be asking the question, Tsuburaya killing of the entire defense squad of the series, and three of the main character's closest friends, one which is a 7-year-old little girl? Surely not... unfortunately, turns out that they would.
Memetic Loser: MAC is often considered the most incompetent defense force in the series, constantly dying and not including some small one off examples, get the least amount of character focus of an defense force team. They are also most remembered for all dying to Silverbloome.
Narm: Episode 26, featuring a prankster alien (looking a lot like a mutated, evil Teletubby) and a shrunken Leo escaping the alien's clutches and looking for Dan. It got better.
A Killer Doll that freezes its victims with its breath might have been scary had there not been footage of it flying.
Special Effects Failure: A lot in this show, due to the 70's oil crisis. That, and budget/schedule overruns in Ultraman Taro. For example, Seven's costume in Episode 1 had no ears.
Bunyo has a human form, a "humanoid" form with green skin, a small alien form, and a kaijuu form. As soon as he transforms from his human form, he tracks slime everywhere.
Silver Bloom's constant use of acid is pretty icky.
They Wasted a Perfectly Good Character: Astra. Despite his role as Leo's long-thought-to-be-deceased brother being ripe for storytelling, his role rarely amounted to anything more than a Deus ex Machina. Even in later series, he ends up playing second fiddle to Leo.
Unintentionally Unsympathetic: While the MAC team getting annihilated by Silver Bloom was very terrifying most of the members if not all of them are pretty much an Aloof Ally to Gen, quick to blame and shun him if something goes wrong (which happens a lot), have no character development, and are assholes in general. So, if one cannot look past these traits, the tragedy that befalls them can be seen as a case of Asshole Victim.
Villain Decay: From the destruction of both planet L77 and Tokyo to the courting of "the most beautiful monster in the universe", Alien Magma lost his edge between Episode 2 and 30.
Vindicated by History: Poor ratings, but a lot of adult fans like seeing an Ultra show this dark for once. It was intended to woo back some adult audiences who disliked Taro's comical tone, but ended scaring young viewers away.
What Do You Mean, It's for Kids? / What Do You Mean, It's Not for Kids?: The series is somewhere between both. On one hand, it shows a lot of gruesome violence and some unexpectedly shocking death scenes more typical of a series aimed for older audiences, but on the other hand, it tends to feature a lot of goofiness and kid characters play a bigger role than one would expect such a dark and mature series to.
The Woobie: Poor Gen Ootori. All he wanted was justice for his home planet and to live peacefully on Earth thereafter. And for that he gets loads of trauma such as losing all of his teammates, the woman he loved, failing to save hundreds of innocents from Silver Bloome, being berated and harshly trained by a crippled Dan
Tohru, who loses his already widowed father in gruesome fashion and then his Nakama, too.
