Awesome Music: The opening theme by Takayuki Miyauchi has a grand, orchestral-style intro intercut with a few fleeting moments of equally amazing rock guitar music. The lyrics are extremely catchy and will definitely get fans excited as they chant the lyrics.
How the Bio Robo uses a real mechanical hand that's to scale with how large the Humongous Mecha is supposed to be to pick up the descendants of the people it imbued with Bio Particles in the past. You can really feel the largeness of the robot with these scenes.
Red One summoning his Fire Sword for the first time (and every other Stock Footage used of it since then). Because special effects were more primitive at the time, they had to use a literal sword doused in gasoline and lit on fire to achieve the practical effects. No CGI fire here!
Awesome Music: The ending credits of Choudenshi Bioman doesn't only feature a happy and catchy theme; it also features the Biomen cleaning the Bio Robot. It's an indelible scene that surely comes up to anyone reminiscing about this series in particular.
The impressive fight choreography between Mika Koizumi/Yellow Four I and Farrah Cat in episode 2 might qualify. Also, the first appearance of Jun/Yellow Four II fits as well, particularly her actress's extensive stunt work that would make Annie from Shaider proud.
The Biomen's sheer amount of Team Attacks from Laser Swords to Gigantic Arrows as well as blasts of concentrated Bio Particles wreaked havoc among the Beastnoids all series long. Their swords also have individual abilities for good measure.
Their Team Attacks were so varied even for a Super Sentai series that had the Biomen faced off against Monsters of the Week instead of a rotation of the same villains, they'd probably massacre them all in creative fashion every episode (as opposed to just shooting a cannon at them every time).
The way Mika takes the Anti-Bio-Particle shots from Mason is heartbreaking but amazing when it comes to how she never hesitates to take them all for the team.
The death of Mika is a true tearjerker but her in-story heroism to save the rest of her teammates from the Anti-Bio-Particle Cannon ultimately inspired them to better harness their bionic abilities and resist their fatal weakness in future encounters.note It also inadvertently better prepared them against the arrival of Silva down the line.
The first arrival of Bio Hunter Silva on Earth, with him taking on both the Neo Empire Gear and the Biomen on his own years before the DragonRanger would do the same thing with Bandora's Forces and the Zyurangers.
Awesome Music: "Shirogane no Karibito" (The Silver Hunter) or Bio Hunter Silva's theme music is quite iconic. Every time it plays, the stakes are upped and anything goes from hereon out.
Silva is also awesome because of his determination to take down the Biomen in a Last Stand even after Balzion is destroyed and becoming the Spanner in the Works that led to the Neo Empire Gear's downfall, with him being directly responsible for the deaths of Farrah and Mason.
The episode starts with the Biomen launching the Bio Robot against Dr. Man's final Neo Mecha Gigan he's personally piloting, KingMegas. The Bio Robot struggles a bit because King Megas has all of Balzion's Anti-Bio-Particle abilities, but they triumph with the help of Peebo's Bio Particles boosting Bio Robo's powers.
After the destruction of King Megas, Dr. Man activates a planet-annihilating Anti-Bio Bomb that was supposed to destroy the whole Earth and everything in it. The Biomen then follow his escape ship back to Neo-Grad. They then face off against the remaining Mecha Clones before killing Farrah Cat inside the base.
Once the Biomen corner Dr. Man in his headquarters, demanding he defuse his bomb, Dr. Man's biological son Shuichi Kageyama arrives and shows him a photo of them and Mrs. Kageyama as a family in a bid to have him remember his humanity.
From there, Neo-Grad gets buried in snow and becomes Dr. Man's mausoleum. Later, Peebo then says goodbye to the Biomen and Shuichi as he embarks on a new journey to the stars, his mission of saving Earth against the Neo Empire Gear finally fulfilled.