5 Ben 10 Powerhouses Who Could Actually Take Down Alien X

Alien X is the kind of character writers invent when they want a giant 'break glass in case of multiverse meltdown' button. He can basically do anything... except act quickly, because his brain is a three-way committee. That tiny crack in the armor is where a few very specific Ben 10 characters might, maybe, possibly thread the needle.

Quick refresher on Alien X

Alien X is Ben's Omnitrix sample of a Celestialsapien from the Forge of Creation. He has three internal voices that must unanimously agree before he does anything: Serena (love and compassion), Bellicus (rage and aggression), and Ben (reason). That consensus rule is why he can be both unstoppable and, sometimes, a statue.

On paper, he's beyond stacked: omnipotent framing, reality/time/space manipulation, molecular creation, telekinesis, telepathy, cosmic awareness, and immortality. He can recreate a universe. He can also rewrite his own weaknesses... as long as the trio inside signs off. That bottleneck is the whole game.

The tiny club that could trouble Alien X

1. Osmosians (think Kevin's species)
   Why they scare him: Osmosians can absorb matter, energy, and even powers, then mimic what they take in. Against a newborn Celestialsapien, that absorption could stick, which is one of Alien X's known soft spots.
   But here’s the catch: a mature Alien X can just turn off his own vulnerabilities. If the three voices agree, he can reality-warp away the absorption problem entirely. In a straight-up fight, Osmosians risk over-absorption (mutation or insanity) and instability from bad energy mixes, while Alien X can simply decide 'nope' and make it true.
   Abilities: matter/energy absorption, power mimicry, regeneration, enhanced strength and durability.
   Weaknesses: over-absorption leads to mutation/insanity; unstable with incompatible energy types.
2. Toepick
   Yes, really: Toepick's hidden face induces uncontrollable, deep-rooted terror. If two of Alien X's three personalities panic, they can lock each other out, and no consensus means no action.
   How X wriggles out: he can just not look, or use reality-warping to negate Toepick's fear effect or alter perception entirely. If the personalities are mid-argument, a nonresponsive X can effectively ignore the trigger.
   Abilities: fear induction by revealing his face, extreme durability, super strength, resilience.
   Weaknesses: the fear blast can accidentally nail allies; he still gets thumped by stronger physical hitters.
3. Vladats
   The vampiric angle: Vladats (from Anur Vladias and Anur Transyl) drain the life force of living beings. That specific drain maps to another Alien X vulnerability. They also do eye-contact mind control and something called Corruptura to puppet others, though how that plays against a Celestialsapien's split consensus is murky at best.
   Why it still probably fails: if Alien X decides to nullify the drain, it's over. Mind control might not stick, and even if it did, you're trying to hijack a mind that requires three voices to agree. Good luck getting all three to cooperate with your orders.
   Abilities: energy vampirism, superhuman strength/durability, wall-crawling, regeneration, electrical manipulation, machine interfacing.
   Weaknesses: vulnerable to energy overload and to devices that block absorption; can be starved by energy deprivation.
4. Darkstar
   The energy glutton: Darkstar absorbs energy and life force. If Alien X is stuck waiting for internal consensus, Darkstar could start siphoning in the meantime and potentially snowball.
   Alien X's veto power: again, if the trio approves, X can just negate absorption as a concept and end the problem. He also has time and reality manipulation to hard-counter pretty much anything once he gets the green light.
   Abilities: energy absorption and projection, enhanced strength, flight, rejuvenation, extended lifespan.
   Weaknesses: he depends on stolen energy; without a steady feed he weakens, decays, or destabilizes.
5. Nemuinas
   The sleeper threat (literally): Nemuinas have dust that puts almost any species to sleep, Celestialsapiens included. Once you are out, they can enter, examine, and manipulate your dreams, even mass-scale, and push full-blown nightmares.
   The timing problem: if the dust lands before Alien X's trio agrees to become immune, he takes a nap and the Nemuina runs the dream. If Alien X preempts it and flips the immunity switch, the dust does nothing. Their powers only work in dream/subconscious states anyway, and they are ineffective on beings immune to mental control or that do not sleep.
   Abilities: dream/sleep manipulation, hypnosis, telepathy, empathy, creation of dreamscapes.
   Weaknesses: limited to dream/subconscious states; useless against targets immune to mental control or that do not sleep.

About that 'magic beats cosmic' argument

You will hear that magic can short-circuit Alien X's cosmic toolkit, and that Professor Paradox (or a DNA Scanner) could force Ben to drop the form. The reality check: Paradox is not your Alien X answer. Even with his time mastery, he literally had to strike a deal to keep his distance from Alien X's personalities. Alien X sits a tier above that, and any 'just revert him' plan still collides with the consent rule inside the Celestialsapien.

So... can anyone actually beat him?

Alien X is designed to be practically unbeatable. The only consistent opening is the internal deadlock. Osmosians, Toepick, Vladats, Darkstar, and Nemuinas all have angles that could matter in very specific circumstances, mostly by exploiting absorption, fear, sleep, or that consensus delay. But once the three voices align, Alien X can erase the problem, rewrite his own weaknesses, and end the fight on his terms. It really comes down to whether anyone can act faster than his committee.