Synthoid-Beast Army
This group was led by Gigaro and composed of mostly humanoid chimeras and other animal-based creatures.

Heavysnake had a humanoid body with a long snake draped over the head area that serves as its arms. He was dispatched to hunt and capture humans for Jamahl. When the B-Fighters destroy the snake, he revealed a second head and pair of arms underneath. The second head could blast lasers from its' mouth. Heavysnake was killed.

Bagma Virus
He could shrink to microscopic size and infiltrate the B-Fighers' Insect Armor and possess them. He could reproduce asexually to control more than one B-Fighter at once. In battle, he shot electricity from his antennae. Bagma Virus was later revived and absorbed by Jagul in the series finale.

The mission of this hunchbacked foe was to gnaw through underground power cables to create a mass panic. He had the ability to roll into a ball and tackle opponents as well as breathe fire.However, he had a phobia of cats, so severe that he ran out of the battle at the sight of one. To cure this, Gigaro forced Garinezu to run through a maze with Jamar soldiers holding cats behind every corner a hundred times. After the hundredth time, his fear was gone. He was killed by Blue Beet.

A sloth monster who lacked any motivation to fight. He could steal others' motivation for himself and did so with Takuya and Daisaku. The stolen motivation was collected in the pouch on his back. He was able to steal the motivation of both Takuya and Daisaku, but the insect power of their B-Commanders brought them back to their senses. He was killed when G-Stag sliced the pouch open to restore everyone's motivation, leaving them free to finish him off in his weakened state.

A pig monster who expelled a white gas that stole human voices, rendering people unable to make any noises other than swine noises and sqealing. In battle he could also breathe fire and zap lasers from his tusks. Blue Beet killed him with the Stinger Blade.

Resembling a praying mantis, her aim was to spread her eggs throughout the city, injecting people with them using her long and spiked tongue. The eggs would increase in size and hatch her offspring inside their hosts. Kamazakiller was killed by Blue Beet's new weapon, the Stinger Drill, using the Strike Blast.

A red-shelled crab and shrimp hybrid who emitted a liquid that changed water into poison. He could deflect shots from his shelled armor as well as blast water as strong pulses. After Daisaku's father tried to stop him from polluting the water, Ebigaanya set him adrift with a bomb aboard his boat. Daisaku overcame his fear of the water and saved his father, and then fought the monster. He was killed by a hot water blast from the Input Magnums, which cooked him and paralyzed him for G-Stag to finish him off with the Raging Slash.

Based on an amoeba, he wears a gold mask with rows of faces canopying it, extending in a starlike pattern. Maskuder disguised himself as a plastic surgeon claiming to render anyone beautiful with the use of his special masks. The masks gave his customers the face of the famous model Mizuzu Shiratori, who happened to be a childhood friend of Mai's. But the masks actually were explosive control devices that let Maskuder control the wearers and detonate them when he broke the mask he wore, which was his central gold face. Under the gold mask he wore was a single eye. Maskuder had the ability to cause explosions on command.

The Moja
Gigaro disguised himself as a salesman and gave several children creatures from another dimension called the Moja. He instructed them that if they started to act up, to hit them with a special stick he gave them. But the stick caused the Moja to become firece creatures that absorbed the consciousness of the one who hit them. The creatures then eventually gathered together and transformed into the moth-headed monster Mojanga.

Mojanga was made of a bunch of Moja, creatures given to children. Mojanga breathed fire and the consciousness of children was trapped inside Mojanga. The children could see to the outside world. Though the children tried to urge the B-Fighters to fight, Mojanga could bring about exactly the reverse of what the consciousnesses trapped inside him said. Eventually Daisaku managed to get inside Mojanga's body and freed the children.

At first, Gagamoth was an energy-sucking caterpillar monster, but when it absorbed the power of the Beet Ingram, Gagamoth transmutated into a red moth monster. In this form, its arms end transformed into duplicates of the Input Magnum and Stinger Blade respectively. It was, soon after, the first to be destroyed by the newly born Super Blue Beet. Gagamoth's first form was later revived by Jagul to fight the B-Fighters.

A monster created from the fictional "Rasbel" flower, a carnivorous plant that had its own mobility and feed on small animals. Although almost invincible, Rasbelga's only weakness was the fruit of a tree discovered by Sayuri, an old girlfriend of Mukai's, which made him regurgitate the people he swallowed. It also robbed him of his pollen spray. Aside from spraying pollen, it could also shoot out vines from its mouth to strangle enemies. Mukai went to stop Rasbelga by donning a bulky armor, calling himself "Mukaider K-3", though the armor fell apart gradually as he fought. Despite this, Mukai's actions enabled Blue Beet to help G.Stag and Reddle, who were stuck within Rasbelga's stomach, to break free and finish the monster.

A monster whose body was covered with bony plates. He could also control the bones that lay strewn around his island, extending them and using them to capture the B-Fighters. Hellsgyra was beaten by the combined powers and strength of Drago and Blue Beet.