In the vast world of That Time I Got Reincarnated as a Slime (Tensura), there is no bond more iconic—or more terrifying—than the one between Rimuru Tempest and his fanatical second secretary, Diablo.
Diablo’s loyalty borders on absolute madness. He views Rimuru not just as a king, but as a supreme, infallible deity. He would gladly turn entire empires into ash just for a word of praise from his master.
But Tensura fans love to ask the ultimate “what-if” question: What happens if Diablo and Rimuru actually fought? If Diablo’s fanatical loyalty was somehow bypassed, who would win in a bloodmatch? Let’s break down the cosmic scaling, their ultimate skill sets, and the definitive winner of Diablo vs. Rimuru.
The Base Scaling: God-Tier Slime vs. Primordial Chaos
To understand how this fight plays out, we have to look at what these two entities actually are at their absolute peak power levels.
Diablo: The Unkillable Concept
Diablo is Noir, one of the seven Primordial Demons who existed before time itself. He has millions of years of combat experience. He doesn’t just use magic; he manipulates the fundamental laws of the spiritual realm. His most terrifying trait is his instant resurrection glitch—if you destroy his physical form or his spiritual core, he simply wills himself back into existence a second later with zero power loss.
Rimuru: The Ultimate Singularity
Rimuru started as a lowly slime, but through constant predation and evolution, he shattered the power ceiling of the universe. By the later stages of the story, Rimuru isn’t just a True Demon Lord—he evolves into a Supreme Deity (Viscount/Digital Nature), effectively matching or exceeding the power of the Creator God, Veldanava.
Skill vs. Skill: How Do They Match Up?
If they were to clash, it would be a battle of reality-warping concepts rather than simple swordplay or energy blasts.
Diablo’s Win Condition: Azazel & Reality Warping
Diablo’s Ultimate Skill is Azazel (Lord of Temptation). This allows him to create an Isolated Battlefield, a pocket dimension where he completely controls the laws of physics.
His ultimate attack is Turn Real to Unreal, which lets him swap illusion and reality. If Diablo convinces Rimuru’s mind that he has died, Rimuru’s physical body will automatically die to match his mental state. Combined with his unmatched combat intellect, Diablo is a nightmare for almost anyone in existence.
Rimuru’s Counter: Ciel & Void God Azathoth
The reason Diablo’s reality-warping tricks won’t work on Rimuru comes down to two words: Ciel and Azathoth.
- Ciel (The Ultimate Mind): Rimuru’s evolved Manas (sentient core AI) computes information at a cosmic scale. The moment Diablo attempts a mental illusion or physics manipulation, Ciel will analyze it, break it down, and counter it instantly. Diablo cannot trick a mind that operates faster than the universe itself.
- Void God Azathoth (Turn Null): This skill gives Rimuru access to primordial destructive energy. More importantly, it features Soul Consumption, an upgraded version of his original Gluttony skill. It allows Rimuru to swallow space, time, souls, and concepts into an infinite imaginary space.
The Verdict: Who Wins?
There is no sugarcoating it: Rimuru wins this fight with absolute certainty.
While Diablo is completely immortal against standard enemies because he can instantly resurrect from the spiritual realm, Rimuru is his ultimate hard counter.
If Rimuru uses Void God Azathoth, he doesn’t just destroy Diablo’s body; he consumes his entire spiritual ego and places it inside his Imaginary Space. Sealed inside Rimuru’s infinite void, Diablo wouldn’t be able to access the spiritual realm to resurrect. He would be entirely cut off from reality.
The Irony: Why This Fight Will Never Happen
The funniest part of this match-up is that Diablo himself already knows he can’t beat Rimuru—and he is completely thrilled by it.
Diablo didn’t serve Rimuru out of pity; he forced his way into Rimuru’s service because he saw Rimuru constantly breaking the pre-determined laws of fate. To an ancient, bored Primordial Demon, serving a master who is fundamentally superior and endlessly unpredictable is the ultimate paradise.
If Rimuru ever ordered Diablo to fight him, Diablo would likely view it as a divine test, give it his absolute all, and then happily accept being swallowed by his master’s void.
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