Diablo in That Time I Got Reincarnated as a Slime is portrayed as one of the absolute top‑tier monsters in the entire setting, and widely regarded as Rimuru’s single strongest subordinate, both in raw power and in tactical, almost terrifying intellect.

Who Diablo Is (Quick Primer)

Diablo is a primordial demon (Noir) who becomes one of Rimuru’s most loyal and dangerous followers after being summoned and named. His evolution, access to Rimuru’s power, and demonic origin all stack into an almost broken combination.

  • He starts as a primordial demon already feared by other demons.
  • After Rimuru names him and later reconstructs his body with Rimuru’s own cells, his growth potential skyrockets far beyond a “normal” demon or demon lord.

How Strong Is Diablo In-Series?

From a pure combat and narrative standpoint, Diablo is insanely strong, even by late‑series standards.

  • He is repeatedly described as Rimuru’s strongest subordinate, surpassing other monsters like Veldora’s allies and the other demon executives in Tempest.
  • High‑end discussions in the fandom and later material place him close to the very highest beings, with only entities like Veldanava (the creator god) and a few others clearly above him; even powerful enemies such as Feldway are forced into retreat.
  • His energy potential is stated in some analyses to rival characters on the level of Guy Crimson, one of the world’s pinnacle demon lords, especially after fully adapting to Rimuru’s cells and powers.

In other words: within Tempest, he is the “final boss” that still works for the protagonist.

What Makes Diablo So Broken?

Diablo isn’t just strong because of big energy numbers; his kit and mindset make him terrifyingly efficient.

  • Hax and energy : He gains access to ultra‑high‑level skills and energies (including void/nihility type abilities in later material), letting him ignore or erase conventional defenses and bypass many normal limitations.
  • Rimuru’s cells : Having his body rebuilt with Rimuru’s cells gives him near‑limitless growth and recovery potential and lets him wield Rimuru’s gifts at a level rivaling almost anyone else.
  • “Beyond death” nature : Later descriptions emphasize that killing him in the usual sense is extremely difficult, because his existence and regeneration operate on a higher system level than most beings.
  • Genius tactician : Multiple sources highlight that Diablo’s real danger is his mind; his tactical and political planning is a core reason Rimuru’s nation rises so fast. He plans years ahead, handles problems before they appear, and treats battles like chess boards.

Put simply, even if another character ties him in raw stats, Diablo tends to win through experience, strategy, and nasty abilities.

How He Compares To Others

Below is a simplified, lore‑friendly comparison to give a feel for where he sits in the food chain later in the story.

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Character General power tier Relation to Diablo
Rimuru One of the absolute strongest beings in the world, with creator‑level hax and absurd evolution potential. Rimuru is still above Diablo overall, but trusts him enough to treat him as the ultimate problem‑solver and trump card subordinate.
Diablo Rimuru’s strongest subordinate, with power and skills that rival top demon lords and approach the highest beings below the creator level. Beats virtually any “normal” high‑tier character and only clearly loses to the absolute top cosmic entities like Veldanava.
Other demon executives (Testarossa, Ultima, Carrera) Extremely powerful demon lords and commanders, each strong enough to terrorize nations alone. Consistently portrayed as below Diablo; none are expected to defeat him in a straight fight.
Guy Crimson Ancient pinnacle demon lord, long considered one of the strongest beings in existence. Some late‑series analyses equate Diablo’s true energy potential to Guy’s, putting them in similar territory, though Guy’s legacy and status remain legendary.
Veldanava Creator god of the world and ultimate top of the verse. Repeatedly treated as on a different, unreachable level; even Rimuru and Diablo are evaluated beneath him.

Fandom / “Trending Topic” Angle

Diablo’s strength is a frequent debate in forums and power‑scaling discussions, especially as newer light novel material drops and pushes his feats even higher.

  • Many fans argue he’s effectively “main‑character level but leashed,” since Rimuru often holds him back or uses him surgically instead of as a blunt weapon.
  • Others like to point out that his influence and scheming matter as much as his power: he reshapes politics, builds Rimuru’s spy/intel network, and quietly ensures Tempest stays ten steps ahead.
  • With each new volume and wiki/stat update, his profile edges closer to “broken” territory, which keeps him a constant trending topic in power‑scaling circles.

TL;DR: Diablo in Slime isn’t just “very strong”; he’s Rimuru’s strongest subordinate, a top‑tier monster whose true energy, hax abilities, regen, and genius tactics put him just below the absolute gods of the setting, and comfortably above almost anyone else you can name.

Information gathered from public forums or data available on the internet and portrayed here.