Alexis・Kerib (アレクシス・ケリヴ, Arekushisu Kerivu) is the main antagonist of SSSS.GRIDMAN. He is an immortal, misanthropic cosmic being who sought to feed on others' emotional suffering and manipulate insecure humans such as Akane Shinjo so he can twist their mental states inside out for such purpose as means to amuse himself.
Alexis was shown to behave in gentlemanly way, speaking in a calm and polite manner. While his dynamics with Akane parallel that of Khan Digifer and Takeshi Todo in seeing her as a tool for his own benefit (a fact that is hinted at by Anosillus II), his relationship with her seemed a more positive one, as he praised Akane's kaiju designs and was visibly shocked by Akane's tantrums, noting this uncharacteristic behavior as "violent". This, however, masked his true color as a parasitic master manipulator who exploited Akane's negative emotions so he could harness those as a power source, having implied that he had done the same on others like her. A hint of this was when he pretended to be polite to Anti before using his own weapon to attack him.
Because of his supposed immortality, Alexis became plagued with deep emptiness which he believed could only be quenched by feeding on others' pain, which he exacerbated by ruining their ideals over and over again.
Alexis・Kerib throughout much of the series had the ability to manifest within the same dimension as the human characters, though when first introduced he appeared on Akane's computer screen similarly as the original Gridman series. He is very tall, towering over the human characters. His coloration is largely black, though his cloak appears deep Royal Blue in some images; the inside of his cloak is red, as indicated by the flare at the base, as is his glowing visor; his mouth, which glows when he speaks, the smoke that emanates from his head, and a pair of shoulder guards that appear to be plating of some kind, are turquoise; he has silver chains with large links wrapped around his shoulders, between the turquoise plating and a large pair of rigid, upward-pointed shoulder guards that match his cloak; on the underside of the large shoulder guards are glowing red terminal lights, with gray cords extending from near where his absent arms should be to his back; lastly, he has another pair of gray cords extending from either side of his mouth to the turquoise plating on his shoulders. His head is an odd shape vaguely reminiscent of a Christmas tree, or possibly a witch's hat.
- Instance Abreaction: Alexis can bring the kaiju sculptures Akane makes to life and set them on the city or anywhere else she wants. He can also use this ability to turn people into kaiju as shown through turning Akane into her alter-ego, Zegga.
- Mass Resurrection: Alexis can also resurrect several fallen with the same ability.
- Attention Manipulation:
- Energy Manipulation:
- Portal Generation:
- Negative Emotion Empowerment:
- Flame Form:
- He was one of the characters in the scrapped show Gridman F, in the same role as he is now.
- Unlike Khan Digifer, who resembles Shredder from the Teenage Mutant Ninja Turtles series, Alexis' design more closely alludes to the following characters:
- Over Justice: The design of Alexis' facial features greatly resemble that of Over Justice from Space Patrol Luluco, another Trigger production. Interestingly, they share the same Japanese voice actor, Tetsu Inada.
- Scourge a.k.a. Black Convoy: Like the majority of characters in SSSS.GRIDMAN, Alexis' design also draws on elements from the Transformers series, namely the character Scourge (ja:Black Convoy), an evil lookalike of Optimus Prime (ja:Fire Convoy) from Transformers: Robots in Disguise (ja:Transformers: Car Robots). In fact, Alexis' body and shoulder guards share the same coloration as Scourge.
- According to an interview with Alexis' voice actor Tetsu Inada, director Akira Amemiya told him that Alexis is neither a cosmic being, nor immortal, but rather the corrupted form of Over Justice himself, specifically his future self. During his thousands of years of multiverse journeying after the fight against Blackholeian, Over Justice became corrupted and turned into Alexis・Kerib until Gridman restored him with use of Fixer Beam. Someday, the exorcized Over Justice may return as Gridman Justice.
- Conversely, it has been said that Inada was just making a joke, which gets lost in the translation, hence it got retold as fact.  This alternate interpretation is based on an interview with Inada in a special edition of Uchusen magazine covering SSSS.GRIDMAN.
- Taking into account of how Alexis' surviving fragment ended up in Gridman and NGJHS' custody, coupled with the aforementioned explanation and the fact he uses Akane as his host to attain his combat form, it's implied that Alexis is the vampiric, demonic personification of Over Justice's inner darkness that must feed on negative emotions of others to survive, but this has yet to be confirmed.