Marvel Comics’ Sentry is one of the most powerful beings to ever walk amongst Earth’s Mightiest Heroes. Having gone toe to toe with the likes of Thor, The Hulk, and Namor, there aren’t many that can compare to the Golden Guardian of Good’s raw power.

But even for a superhero regularly seen as 'Marvel's own Superman-level superhuman,' all that power doesn’t make Bob Reynolds entirely unstoppable. And for all his great strength, these are the Sentry's biggest weaknesses pulled straight from Marvel Comics.

11 Negative Zone Energy

For all his vaunted power, the Sentry is as vulnerable to the Negative Zone as any other Marvel Hero, if not more so. As established in Sentry #3 by Paul Jenkins, John Romita Jr., and Mark Morales, prolonged exposure to the Zone incapacitates Bob with the N-Space effect – a crippling onslaught that renders the Sentry both physically powerless as well as emotionally overwhelmed.

Venturing into the Negative Zone with the Hulk at his back, Sentry quickly begins to lose his considerable power before he and the Jade Giant are run off by the deadly Void. With such an immediate effect, anyone who can weaponize Negative Zone energy is a considerable threat to the Golden Guardian of Good. And with N-Zone ne’er-do-wells consistently attacking Earth-616, it’s not the most convenient weakness for Reynolds to have.

10 Human Biology

Bob may wield the power of a million exploding suns, but his basic physical form, no matter how powerful, is still human at its core. As such, the Sentry has all the typical weak spots and pressure points associated with a standard human – they just have to be struck with sufficient force. In a knockdown brawl with Hercules himself, Sentry was temporarily incapacitated by a particularly low blow, and he’s even been knocked out by powerful enough opponents like Blue Marvel.

Against any enemy strong enough to be considered a physical equal, Reynolds still has to take care to fight with actual strategy as opposed to blind luck and sheer strength. He may be the ultimate endpoint of the Super Soldier Serum, but Sentry is still built like an ordinary man.

9 Asgardian Magic

Like his super counterpart from the Distinguished Competition, the Sentry isn’t totally invulnerable to certain forms of magic. While most traditional forms of energy actually fuel the Golden Guardian, Bob’s powers don’t do much to aid him against certain eldritch energies – particularly those that hail from the Realm Eternal, Asgard.

During the Siege of Asgard, a group of Norn-stone-empowered Avengers managed to do some serious damage to the Sentry while in his Void form. And Thor himself was even able to kill this corrupted Void using the might of Mjolnir. Considering Sentry was able to literally dismember a similarly magic-empowered Ares during this Siege, it’s clear that Asgardian magic has a specific effect on Reynolds. And should he ever battle Asgard once more, the end result could be the same.

8 Naivete

The Sentry is one of Marvel’s ultimate heroes, but at his core, he’s a teenaged Bob Reynolds’ idealized notion of what a hero should be. In Bob’s mind, “good” and “evil” are simple, inalienable concepts that aren’t open for interpretation, and this cookie cutter notion of right and wrong has made him vulnerable to manipulation on more than one occasion.

The Void, considers this to be one of Bob’s greatest weaknesses, and it’s not hard to see why after his naivete that partially drove him to side with Norman Osborn’s own Avengers during the Dark Reign, And when facing off against the Frank Castle in Punisher #1 by Rick Remender, Jerome Opeña, and Dan Brown, Punisher escaped by bluffing a bomb threat that he knew Sentry would have to check.

7 Knull

The God of Symbiotes is one of the biggest bads that Marvel has ever brought to bear, and even the Sentry fell victim to the power of the King in Black. Able to manipulate the Void’s dark nature, Knull tears the Sentry in half, claiming that Sentry’s inner darkness bows to him in King In Black # by Donny Cates, Ryan Stegman, J.P. Mayer, and Frank Martin.

It’s not totally clear if this sort of Void/darkness manipulation is an ability that was exclusive to Knull, or if the same route could be taken by any sort of all-powerful being of darkness whose shadowy energies outpace Bob’s. But at the very least, there will always be one King in Black that could potentially take down the Sentry in a similar fashion.

6 Chi Powers

Asgardian magic isn’t the only mysticism to which the Sentry is vulnerable as he’s shown a particular susceptibility to the Chi-based attacks wielded by the warriors of K’un-L’un.

Black Panther and the Agents of Wakanda #2 by Jim Zub, Lan Medina, and Craig Yeung pits the titular team against a Void-merge Sentry as his haywire energies unknowingly begin to warp reality around him.

Distracted by Thor, Reynolds is left open to a Chi attack – the Sevenfold Strike of the Annihilated Aura – by Fat Cobra. This strike incapacitates Sentry, freeing him from these evil energies and ending the fight, but the logic behind the effectiveness of such an attack makes total sense. After all, these Chi attacks are all about the redistribution of power, and using the Sentry’s own energy against him must be incredibly damaging.

5 Anti-Matter

While the Sentry can be fueled by most forms of energy, he’s demonstrated a lack of proper defense against anti-matter and anti-matter radiation. Having gone head-to-head against both Blue Marvel and Anti-Man in Adam: Legend of the Blue Marvel by Kevin Grevioux, Mat Broome, Sęan Parșon, and Alvaro López, Sentry was defeated handily in both confrontations.

Considering his reliance on energy from his positive matter universe, and his pre-established weakness to the energies of the Negative Zone, it’s not surprising that he’s vulnerable to yet another form of negative energy. While anti-matter doesn’t have the same debilitating results as the N-Space effect, its s are two of the only beings to ever genuinely defeat the Sentry in a contest of strength, and that makes them that much more dangerous.

4 A Need for Energy

In many ways, the Sentry is essentially a living battery. Unlike Superman, however, Bob’s draws upon more than just the energy of the Sun – he can absorb practically any energy source. Unfortunately, this isn’t just an added advantage, but a weakness as well, because the Sentry flat out NEEDS energy to empower him.

Once that energy is used up, so too is Bob Reynolds’ Sentry form. A prime example of this would be Sentry’s battle against the Jade Giant in World War Hulk #5 by Greg Pak, John Romita Jr., and Klaus Janson as Marvel’s two strongest heroes battle each other to a depowered standstill after expending their tremendous reserves of energy. Wielding the power of a million exploding suns is quite draining, even for a being like the Sentry.

3 Psychic Attack

Despite his considerable physical power, the Sentry’s mental fortitude has always been one of his primary weak points. Between his personal struggles with his mental illness to his deep-seeded fear of his alternate Void persona, Bob Reynolds’ is incredibly vulnerable to telepathic manipulations and psychic attacks. And on more than one occasion, Sentry’s vulnerability to battles of the mind has been his downfall.

The primary example of this would be his encounter with Mastermind, the malevolent mutant who used his considerable psychic talents to manipulate the Sentry into erasing himself from the memories of everyone on Earth for fear of his own destructive potential. With such raw power at his command, Reynolds’ fear is somewhat justifiable, especially considering his unstable history. But it’s this same fear that leaves the Sentry’s mind especially vulnerable.

2 Mind-Altering Substances

As with his vulnerability to psychic attacks, it’s once again the Sentry’s own brain that puts him at particular risk to the effects of LSD and potentially other mind-altering substances. Aside from Bob Reynolds’ own history of addiction, this is a threat that he’s gone up against in his own rogues’ gallery – specifically against the criminal known as The Hippy.

Sentry #2 by Paul Jenkins, John Romita Jr., and Mark Morales reveals a specific instance in which the Hippy triumphed over Sentry by forcing him to drink an entire lake’s worth of LSD, entirely manipulating Reynolds’ sense of reality for over a week. And with the Sentry’s pre-existing ability to manipulate reality, often subconsciously, this sort of attack presents a major threat not just to Bob, but to the world at large.