"It's a potion I've invented where, when the patient drinks it, he turns into a axe-wielding homicidal maniac. It's basically a cure... for not being an axe-wielding homicidal maniac! The potential market's enormous!"
Cowboy Bebop has the Red Eye serum, which speeds up reflexes to superhuman levels and allows perception in Bullet Time. However, withdrawal causes vomiting, trembling, and bloodshot eyes, hence the drug's name. Julia proudly displays Red Eye paraphernalia on her windowsill. Asimov Solensan uses a high-grade variant when flying high-speed spacecraft.
Use of the B303 Devilfish of Eureka Seven requires the wearing of a painful-looking apparatus on the head that shoots reflex-enhancing drugs straight through your sinuses. It is stated to be outright required in order to humanly operate the machine, which has no performance limiters, or defense for that matter. For obvious reasons it's mentioned not-so-subtly that this is something you would not want to use on a regular (let alone semi-regular) basis.
Also, Anemone takes - or is forced to take - injections of some sort of Psycho Serum for piloting TheEnd, which suppresses her headaches but makes her psychotic and vicious. She quits it by the end of the series.
AKIRA likewise has super drugs that either give Psychic Powers or kill the user messily, the latter being the more common result. Tetsuo is dependent on these at first but gives them up after discovering that they dampen his potential.
In Black Cat, one minor character drank the Tao juice, allowing him to access a superpower. For him, he could increase his muscle mass drastically, eventually being able to block bullets with his biceps. When he comes across the heroes, he loses, and returns, putting his whole being into increasing his muscles. He dies from using too much energy, and degenerates into a shriveled husk.
Well...it covers insanity (and by this universe's extension, alas, evil), addiction, theoretically shorter life expectancy, and super-powered evil side.
Insanity and evil are only synonymous in the Anime. In the manga, madness is handled differently.
Gasaraki has the Eyeglobulum, which when injected into a person give them the same quantum abilities as Yushiro, enhancing the way they pilot their Mecha, however as a side effect which always occurs, namely that said person will quickly turn psychotic, adopt animalistic behaviour and have psychic nosebleeds, with a 25 percent chance of lapsing into a coma and a 50 percent chance of dying from cardiac arrest.
Witch Hunter Robin has a green liquid that prevents military meninblack from being harmed by witch powers... until they go insane/scream/flip out.
Mobile Suit Gundam SEED has Gamma Glipheptin, a stimulant given to the Earth Alliance's enhanced pilots that boosts their stamina and reaction speed, but has horribly painful withdrawal symptoms (and since only the Alliance can make it, the pilots can't defect). The chemical is the primary reason for the trio's Fan Nickname "The Druggies".
A modified version appears in Mobile Suit Gundam SEED Destiny. By this point, the drug has been refined to the point where it takes a full days' withdrawal to kill the user, and not the few hours from SEED. The results are Super Soldiers who while less powerful than the original trio, are saner, and thus able to follow orders and go undercover more effectively.
Orochimaru of Naruto created this effect in his finalized curse seal. When activated, it releases an enzyme into the user's body that greatly enhances strength, speed, and chakra levels even before activating the second stage's horrific transformation.
Side effects include near-berserker aggressiveness, rapid chakra depletion, and insanity given prolonged usage. A rare side effect may cause complete disintegration of body while still alive. Nine of ten recipients note cases of sudden death due to curse seal application. Curse seals are not for everyone; don't check with a doctor as Orochimaru will give you one anyway.
Also, the "candy" Caesar Clown gives the kids he kidnaps to Punk Hazard. They are part of a project to create giants, so over long exposure, these kids grow to enormous sizes. It also makes them drug addicts, and they go crazy and will die if denied the "candy" for too long.
The later arcs of Tokyo Crazy Paradise revolve around a drug that greatly increases physical abilities while either driving users insane or rendering them highly suggestible.
City Hunter has Angel Dust, basically an exaggerated version of the Real Life drug with the same name (also known as PCP). Taking it gives Super Strength, invulnerability to pain (to the point the only way to take the subject down quickly is to destroy the brain or behead him. If you don't hit the right spot, a subject may even survive an headshot for a few seconds), and can prolong a dying man's life long enough to heal lethal wounds, but as side effects the subject won't register any damage he suffers and bleed out faster as he moves, the Super Strength is obtained by disengaging the natural limits that prevent the muscles from tearing the human body apart, the subject is easily brainwashed, and withdrawal symptoms will cause a seizure and kill the subject almost all times. Of all those who were given the drug, only two survived both the mission and the withdrawal, and one of them ruined his arms with his own temporary Super Strength and a powerful electrical shock.
In the CCG Magic: The Gathering, most Red/Black creature enhancing abilities tend to take this route. Take, for example, the flavor text of Brute Force, the reimagining of Green's iconic Giant Growth: "Blood, bone, and sinew are magnified, as is the rage that drives them. The brain, however, remains unchanged — a little bean, swinging by a strand in a cavernous, raving head."
The classic Unstable Mutation. +3/+3, but takes a cumulative -1/-1 penalty every subsequent turn — and Defence 0 means death.
Batman villain Bane used the drug Venom to boost his already considerable strength to titanic levels. In the animated continuity he eventually withered into a coma from overuse. He gave up the drug for years in the comics, but post-reboot he's back on the stuff.
Venom was originally introduced as a Super Soldier drug. Batman became addicted to it, which caused him to become violent and prone to crazy laughing fits. He had to spend a month isolated in the Batcave to beat the withdrawal and addiction. Variants on the drug in that same story would kill anyone who tried to get clean after just one dose.
And predating Venom is the "Monster Serum" made by Hugo Strange, first in the Golden Age, but eventually re-introduced into modern comics. The subject becomes larger and more powerful than Bane; the Golden Age version made Monster Men strong enough to tear out elevated train supports, but reduces the subject's mind to little more than that of the stereotypical caveman's.
Deadpool is a Marvel example. Originally Wade Wilson, a mercenary dying of cancer, he elected to be given an artificial healing factor to help cure his cancer. It didn't work all that well. He received a healing factor but as a side effect his cancer got turned Up to Eleven, meaning that his entire body is constantly in flux between being eaten by cancer and being healed. Also the process seems to have left him very, very, very insane, though he would consider that a benefit.
Hourman from The DCU used the drug Miraclo to gain superpowers for one hour, overused it, and became addicted. Though he's since beat the addiction, he continues to fight crime with the drug, constantly battling his old habits.
It's rather more complex than that. An element of the classic story was that Hyde got stronger as Jekyll got weaker (Hyde's drives give Jekyll strength, while Jekyll's morals only restrain Hyde). By the time of the first League book, Hyde is a superpowered ogre because Jekyll is reduced to a sickly, emaciated wreck.
Members of Weapon X and related programs in the Marvel Universe were subjected to this to enhance their strength, stamina, and government-instilled psychoses. As Nuke says, "Gimme more reds! More! MORE REDS!!!!"
Subverted in Nuke's case; the "Reds" and "Blues" are actually placebos. He was driven insane by Wolverine as part of the process of turning him into a killing machine.
The Green Goblin's juice seems to cause dissociative identity disorder in exchange for super strength and rapid healing.
The Hobgoblin claimed that his version of the Goblin formula was perfected to remove the insanity. On the one hand, he did test it on another subject and altered the formula before he took it himself. On the other hand, well, he was the freaking Hobgoblin, and suggesting he was nuts was his Berserk Button. Something of a moot point, since he died and took the formula variant with him.
The serum was perfected (aside from the green skin thing) for the She-Hulk.
Empowered has a variant — Mayfly gives you Mad-science level genius, at the cost of filling your brain with tumors that kill you within forty-eight hours. And that's only when it works — which is point two percent of the time. Mostly it just kills you.
FX 7 in No Hero is based off of a psychedelic drug already. So, not only does it give you super powers but it makes you have living nightmares and many of the Levelers had to get into Downers to counter the drug. Oh yeah, there's also a chance that it could make you explode when you first take it.
Daniel Clowes parody of Captain America, "The Battlin' American" goes through heroin-like withdraw symptoms if he doesn't get a regular dose of supersyrum. Too bad the thugs who steal it from him don't know about this.
This is primarily why attempts to reproduce Prof. Erskine's work in Project Rebirth that created Steve Rogers' enhancements into Captain America proved a continual failure. The known list of failures in the main Marvel universe is:
295 African-American soldiers who volunteered to be test subjects. The experiments produced five Super Soldiers (of them, only Isaiah Bradley, also known as the Black Captain America, survived their missions in World War II), but were unable to reproduce the original serum;
soldier Clinton McIntyre was given the actualSuper Serum against Erskine's authorization... Only for him to go berserker with pain and then having an heart attack: as Erskine and the director of Project Rebirth knew but McIntyre and the general who gave the serum didn't, the subject needed to take a series of additives before the serum and the Vita-Rays. Due him having taken part of the real deal, AIM was later able to repair his body and make it as he had taken the Super Serum;
William Burnside, the Captain America of the 1950s, took a Nazi version of the Super Serum. Thanks to it he became stronger and faster than Cap, but without the Vita-Rays he was slowly driven mad;
Omega Red, a Soviet counterpart with carbonadium tentacles. In his case, the serum gave him Cap's abilities... At the price of wrecking his immune system, forcing him to drain others' life force to avoid dying of some illness, cancer or just complete collapse of his immune system. Luckily for him, Omega Red was given the failed serum precisely because he already had the mutant power of draining life force, with the tentacles focusing his power and the carbonadium, in conjunction with a device called Carbonadium Synthetizer, having the ability to repair his immune system (for obvious reasons, Omega Red is desperately searching the Synthetizer).
The Sentry took "the Professor's secret formula" to become the Golden Guardian of Good, at the expense of developing a second, independent persona, the Void, that was the world's greatest villain. Later it was revealed that the Sentry was originally a junkie who broke into a lab and swallowed a random tube of chemicals to get high.
It's never made clear if Robert Reynolds's agoraphobia is a symptom of the serum or something he already had. Regardless, he's developed much more severe mental problems from being the Sentry.
Deathstroke was the result of the military's experiments in producing a Super Soldier. The formula used left him a crippled wreck for months or years, with brief periods of increased strength and intelligence. Later, after the military cut him lose, Slade revealed that he'd started faking the bouts of weakness at some point to get out on his own.
Deathstroke's son, the first Ravager, was given treatments by the Hive to turn him into Deathstroke's equal. Unfortunately the treatments ended up killing him, which was the Hive's plan all along.
Deathstroke's Psycho Serum has been shown to drive anyone else using it insane, including his wife, his daughter, and Batgirl. At one point the serum also granted its users immortality, but this has been glossed over in recent years.
In the X-Men titles of the early 2000s (Grant Morrison's run) there was the super-steroid Kick. It turns pathetic mutant-wannabe nerds into the U-Men, vivisection-happy domestic terrorists. It also turned Xorneto into someone willing to recreate the Holocaust against the ordinary humans of New York, when the real Magneto would NEVER go that far (Ultimate Magneto, on the other hand...). It was responsible for Quentin Quire's temporary Ascension to a Higher Plane of Existence following the chaos of Open Day. What do you expect for something made at least in part from Sublime, a 3-eon-old Eldritch Abomination?
Imperfect Metamorphosis: Marisa utilizes what is apparently a rather excessive amount of magic-boosting concoctions prior to the mass brawl against Yuuka. She, a Badass Normal in comparison to her comrades in the fight, is the only member to make it out of the whole snafu unscathed, at least by Yuuka herself: she's bedridden with intense nausea and hallucinations from the aftereffects later.
The Crazies is based on a psycho serum being released into the local watershed.
Not a serum, but a surgical technique, is used to ease the agony of burn-victim Darkman, soon after his near-death at the hands of Mafia thugs. Unfortunately, the severing of spinal tracts that carry pain signals to his brain also causes extreme moodiness and bouts of uncontrolled rage.
Emil Blonsky in The Incredible Hulk. Though in his case, it isn't serum but Bruce Banner's blood sample that grants him both power and loss of sanity. He gets two shots of Super Serum over the course of the film but that just makes him Drunk on the Dark Side enough to want Banner's blood in him as well when the time comes in order to get his fair rematch with the Hulk.
The film version of The League of Extraordinary Gentlemen reduces Doctor Jekyll's serum to this, leaving out the psychological explanation. One particular moment that breaks some viewers Willing Suspension of Disbelief has an enemy Mook downing a whole bottle of the potion to become a gigantic version of Mr. Hyde...which makes no sense, as all the potion is supposed to do is release your evil side. Drinking a larger amount shouldn't really make a difference.
Possibly the normal dosage eliminates a person's good side, but spares the neutral aspects of one's personality along with the evil? An overdose could suppress good and neutral both, meaning that not even basic self-preservation instincts would remain to keep the evil side under control.
This was Dante drinking it, The Dragon for Moriarty. Not only was he drinking the attempted replication of the Hyde formula, and a whole lot of it, I imagine that he's got considerably more malevolent natural tendencies than Jekyll. And also remember that while Hyde might be a monster, he has his redeeming moments. Especially since both sides affect the other, it would make sense if they did so passively, too: Jekyll's mind seeps into Hyde's personality, even if his body is weak.
Max Payne, has Valkyr redesigned into a super-soldier serum. While it initially shows promise in granting soldiers increased focus, stamina, and reaction speed, repeated or prolonged use ultimately results in a schizophrenia, delusions, and ultimately, homicidal behavior. In the climax, Max intentionally overdoses on Valkyr for his Roaring Rampage of Revenge, becoming completely unstoppable. He almost dies when the effects wear off, saved only by Heroic Willpower.
Mr. Tony Montana of Scarface fame achieved partial-implacability through the heavy use of cocaine, which also caused his estrangement from his wife and the death of several of his friends.
The Reavers in Serenity were the result of an experimental drug pumped into the air on the planet Miranda. The Pax killed most of the population, but some had the opposite reaction, becoming mindlessly aggressive.
In Scanners, Ephemerol is originally introduced as a scanner suppressant. We discover later that Dr. Ruth originally developed it as a tranquilizer for pregnant women, and that unborn children who are exposed to it become scanners.
In Scanners II The New Order, Ephemerol 2 is highly addictive, and severely debilitating long-term to the scanners. Why they don't just use the earlier version of the drug can best be chalked down to plot convenience.
In Oz: The Great and Powerful, the sinister Evanora effectively gives this (in the form of an apple) to her sister Theodora, ostensibly to ease pain so they can help protect the Emerald City from their enemies. The recipient learns too late that it also renders one heartless and hideous...thus the Wicked Witch of the West, more powerful and vicious than Evanora, is born.
The Spice in Dune is a cornerstone product: it gives a host of benefits like longevity, higher intelligence, and the possibility of Psychic Powers. It is vital to interstellar travel, as Navigators of the Spacing Guild require huge amounts of it constantly in order to perceive the "higher mathematics" needed to safely guide their ships. Drawbacks include addiction, vivid blue eyes, Psychic Dreams for Everyone, risk of death from overdosing or withdrawal, mutation into zero-g floating Fish People (for Guild Navigators) and a crippling galaxy-wide dependence. On the planet Dune, the source of the spice (which must flow), addiction and the blue eyes are the only main problems, though.
Imriel gets a surprise dose of this in Kushiel's Mercy. Ironically, being flat out of his head for a month turns out to be the best thing for him, given the situation that he's in. Being mad for a month makes him immune to the spell being cast on everyone else in the city.
Andre Norton's Sargasso of Space described "crax seed," apparently chewed like tobacco (there's a reference to someone having spit out a crax cud). While high on it, you're lots faster, stronger, and smarter than normal. When you come down, you come down hard: "What occurred to them later was not pretty at all."
In Stephen King's book, Firestarter a government organization called the Shop uses a drug called Lot Six on college students (they tell them that it's a harmless hallucinogenic). Lot Six causes the participants to develop various supernatural powers, such as telekinesis and mind control, but out of the twelve participants, two die right away, two go insane, and five eventually commit suicide because of it.
Doctor Who had this in "The Fires of Pompeii". Breathing in the special hot spring vapours would give a person psychic powers, and with time and repetition, turn them into a giant creature made of rock.
The famous comic book artist/writer Isaac Mendez from Heroes used heroin to access his clairvoyance. He later went clean and learned to use his power sans-drugs.
One episode of Law & Order: Special Victims Unit featured several rapes committed by soldiers due to the aggression-enhancing effects of experimental battle-stims disguised as a malaria vaccine.
The Lost Girl episode "Raging Fae" concerns a human prize fighter whose protein shakes are being secretly spiked with Fae sweat which allows him to Hulk Out. Unbeknownst to him and the Fae spiking his drinks, the enhancement is giving him increasingly frequent rage blackouts and slowly killing him.
The Wraith enzyme in Stargate Atlantis confers strength, increased sensory ability and resistance to Wraith weapons at the cost of the user's sanity after a prolonged period of use, and harsher withdrawal symptoms.
The armbands SG-1 uses in the episode Upgrades give increased physical and mental abilities, but impaired judgment and reasoning. Also, they could not be removed. I don't recall an addiction, though.
The Sarcophagus is very useful for curing illnesses, injuries, and, y'know, death, but can cause severe addiction and nasty withdrawal symptoms, as Daniel Jackson found out in the episode Need.
Repeated use steadily causes insanity. It's mentioned that this is probably why the Goa'uld are so unbalanced...and thus why they are Genre BlindCard Carrying Villainsto a man (except for the Tok'ra, who don't use the Sarcophagus for this exact reason...Q.E.D.). Genetic Memory ensures that their offspring inherit their madness too.
Sam Winchester of Supernatural spent half the season break between three and four, and all of season four, using demon blood to enhance psychic powers conferred upon him by feeding him demon blood as a baby. This allows him to kill demons without necessarily killing their hosts, a power no one else in the setting except angels ever demonstrates, and angels rarely bother. There turn out to be three definite problems with the system:
One, the woman providing him with it is engaged in a long-term manipulation to help the current Big Bad with her Thanatos Gambit to free Lucifer.
Two, most definite an unavoidable problem: The stuff is incredibly addictive, and his growing addict behaviors are not good for any other part of his emotional life.
Three, it apparently is, to some degree, slowly turning him into something other than human. To what degree his bad behavior stems from this instead of straightforward addiction is impossible to determine; he never seems to approach outright Transhuman Treachery, and he demonstrated a capacity for being dangerously obsessive before he started on the stuff. A majority of his choices were actually pragmatic logic for the greater good, but they sure wrecked his relationship with his brother, who has this weird power to be right about everything even when it's for the wrong reasons.
He in fact described it as "a cure for not being an ax-wielding homicidal maniac!"
In the Tabletop RPGRifts, one of the character types is "Juicer". A juicer has a device that continually delivers a cocktail of drugs into his bloodstream, granting him super strength, reflexes, and senses. The catch? It's instantly addictive, and withdrawal can be fatal. If they don't quit, the drugs will kill the user within seven years of starting. Also, he rolls a percentage to see if the drug causes one of several mental disorders.
There are also the Crazies, who gain superhuman strength via brain implants, at the cost of sanity.
Fungus brew in Warhammer Fantasy gives the goblin chugging it superhuman (OK, supergoblin) strength. It also turns them into a gibbering lunatic who has to be subdued by the rest of his unit sitting on him until the enemy get close enough, at which point said goblin is hurled at the enemy and left to rotate around the field for the rest of the battle, pulverising everything he crashes into with an Epic Flail... until the brew wears off (causing a brief demonstration of a spiral in action), or the goblin crashes into a tree, is pulled down by sheer weight of numbers, or gets shot by the enemy/his own side (depending upon tactical needs). A hero with the Madcap Mushrooms can make this even worse for whoever gets hit.
As with everything, Warhammer 40,000 doesn't so much run with this trope as shoot it into space. Too many factions to count in the Imperium use versions with the most famous being the Eversor Assassins, who are injected with such a vast and volatile concoction of Psycho Serums that they not only have to be kept unconscious between missions due to being dangerous and deranged even by Imperium standards but explode when killed. Then there are the Chaos and Dark Eldar versions, which are impressive not only for their tendency to be made from human remains but their ability to turn already daemonically-enhanced, Ax-Crazy psychopaths more insane and into even more brutal combatants, the Emperor's Children Legion in particular known to have about fifty percent of their bloodstream composed of nothing but combat stims.
The plot of Batman: Arkham Asylum involves a chemical called Titan, derived from Bane's Venom formula. The Joker uses it on a few henchmen and gives some to Poison Ivy before using it on himself.
In the BioShock series, ADAM, unstable stem cells harvested from a sea slug, lets users rewrite their DNA to give them all manner of superpowers, from fireballs to computer hacking to shooting bees from their hands. Naturally, it quickly becomes a very highly sought-after resource in Rapture, and despite the obvious dependency issues and the tendency of users to become hideous mutants with hooks for hands (an acceptable cost), the struggle for control of it quickly tore the city to pieces.
Oddly there is no in-game penalty for using plasmids or tonics when the protagonist uses them. Possibly justified since he is a genetically engineered Tyke Bomb, it's likely Jack was designed to be able to use ADAM with few, if any, ill effects. Either that, or he just hasn't been using them long enough for the side effects to occur.
The side effects on the protagonist are hinted at in the good ending: while on his death bed he appears to be suffering from some form of Parkinson's, unable to sit still, and his skin is showing some pretty severe damage.
Also evident in the slippery slope leading to the bad ending. Killing more than two little sisters, even if you save all the others causes you to jump over the Moral Event Horizon and turn into a ruthless power hungry monster killing them all, taking over Rapture and stealing a nuclear submarine. Harvesting gives you more ADAM than saving and if everyone else who used ADAM turned insane, why should you be any different?
Overuse of Superadine is what turns people into Trolls in City of Heroes. Side-effects include green skin, hair loss, growing horns, developing super strength, and becoming a big dumb brute. In rare cases, causes horrifying visions into alternate realities.
The Council loves this stuff. By level 30, most of their troops have been given dozens of supersoldier serums augmenting everything from strength to height, at what is hinted to be a great cost of free will and intelligence. Nictus Fragments either turn you into a barely sentient warwolf or provide minor dark matter generating powers before an alien awarenesstakes over your entire nervous system in a fit of unadulterated evil. Shadow Cysts are a planet-wide version of the Psycho Serum concept; they allow Nictus free access and seem linked to the opening of Pandora's Box, which empowers Heroes, but enough of them cause the entire planet to be overwhelmed in darkness and every sentient being to turn into warwolves.
Freakshow have a cocktail of different drugs of all types, but Excelsior is the real Psycho Serum of the bunch. Thanks to an experimental Crey military booster drug, Freakshow can regenerate from normally lethal wounds, augment themselves with questionably sanitized cybernetics, and come back from the dead. Those that weren't already insane before joining the Freakshow are universally driven off the brink by the drug's side effects and nasty withdrawal, and most Freakshow carry around packs of the stuff feeding directly into their veins.
The Lost and the Rikti are intentionally exposed to a nasty and powerful mutagen causing extreme physical deformations and psychic powers, at the cost of drastically changing entire modes of thought and eventually hooking the user up into the Rikti psychic network, driving them against normal human society. Oh, and the physical deformations ain't pretty.
Arachnos Tarantulas were once human beings, doused in chemicals, and hooked directly into machinery that could not fit a whole human body. The Tarantula Queens are defined as those who came out of the process with two things: amazing psychic powers, and crippling insanity.
Hamidon himself picked up a Psycho Serum that turned him from a human-hating man into a human-annihilating giant jello blob of death; he was probably mad to start with, though. His followers, the Devoured, are normal humans who may or may not have liked the Devouring Earth's demands, and turned into freakish monsters with amazing powers but utterly subservient to Hamidon's insanity.
The Infected and the Contaminated drank sewer water and Rikti drugs, respectively. Results may include glowing eyes, superhuman resistance to damage, electrical powers, and a desire to bring down society.
Krylov's Creations invert the concept; they started out villainous, took the relevant Psycho Serum to gain powers, and either went on a mad killing spree in a villain lab or decided to go play hero... while being slightly insane.
The Well of the Furies itself can be a Psycho Serum, as it empowers whomever imbibes it's waters with the powers of a random deity. There are three characters known to have imbibed directly from the Well of The Furies.
Marcus Cole: A.K.A. Statesman, who received the powers of Zeus. This granted him Flying Brick powers with a side dose of Shock and Awe.
Stephan Richter: A.K.A. Lord Recluse, who gained the power of Tartarus. This caused him sprout spider legs out of his back and become increasingly sensitive to sunlight, though he did get a major strength and intelligence boost.
And the most compelling case of all... Stheno, Goddess of the S'lisur. A Giant Snake Monster that rules over Other Snake Monsters. The Well of the Furies doesn't seem to have a very good track record so far... And don't even get me started on Tyrant and the Reichsman...
In The Elder Scrolls IV: Oblivion, a certain rival guild is discovered to be using Hist Sap, a revered substance in its homeland and a powerful Psycho Serum. A good deal of quests in one storyline deal with infiltrating the group to find out its secrets, during which you take some Hist Sap and kill a village, thinking they were goblins. Even if you know it's coming, you can't avoid it.
Even After the End, the Fallout series is chock full of such 'chems' as buffout, mentats, stims, med-x, jet and, yes indeed, psycho! While a range of side-effects from temporary stat penalties to damage occur immediately upon taking them, and a chance of becoming addicted (which will cause further stat penalties if you go without them too long, accumulating repeatedly until withdrawal is completed) exists, there is one exception: It's a-ok to regularly pump yourself full of fistfuls of the completely side-effect free standard size stimpacks every single day.
And with your stims, be careful on the recommended dosage; too much, and while you'll regenerate like a Ghoul in a reactor, you're going to get the side effect of Stim Sickness.
Far Cry revolves around the Mad Scientist Dr Krieger who developed a mutagen that enhances every organ in the body but turned the subjects into ultra violent killing machines - the Trigens.
In Final Fantasy VII and its associated works, cells from Jenova (the game's Eldritch Abomination) are frequently used to give the subject enhanced physical abilities (e.g., strength, speed, durability, etc.) as well as unusual powers. But those same alien cells also frequently cause varying degrees of psychological instability and/or gross physical mutations, depending on the amount and the method of infusion, as well as the specific individual involved.
Regular SOLDIERs such as Zack are carefully screened and selected for both physical and mental fitness by Shinra. They develop superhuman combat abilities after being subjected to a combination of Mako and Jenova cells, but don't appear to suffer any noticeable side-effects. The only visible abnormality from their transformation is slightly glowing eyes from the Mako infusions.
Sephiroth clones, Cloud included, were subjected to Mako and Jenova cell treatments similar to SOLDIERs. However, since they weren't screened for mental stability like normal SOLDIER candidates, Sephiroth Clones generally suffer severe personality breakdowns and become vulnerable to Sephiroth's mental control. They're frequently seen hunched in black robes, muttering disjointed phrases related to Reunion, Jenova, and Sephiroth.
Cloud also received enhanced physical abilities from the Sephiroth Clone experiments, which helped make his claim of being an actual SOLDIER believable.
Special research prototypes such as Sephiroth, Angeal, and Genesis were subjected to significantly more extreme experiments involving Mako and Jenova cells. On top of the expected enhanced physical abilities, they also develop various special powers (e.g., Angeal's ability to absorb other creatures as well as produce Angeal clones, Genesis's ability to transform others into Genesis Clones, etc.). However, the presence of extreme amounts and/or types of Jenova cells in their bodies probably resulted in all three developing varying degrees of mental instability (e.g., Sephiroth's descent into insanity at Nibelheim, Genesis's obsession with 'the gift of the Goddess', Angeal's suicidal self-loathing, etc.), as well as blatant physical mutations (e.g., Sephiroth's cat-like eyes, their ability to manifest a single wing, Angeal's ability to absorb and fuse with other creatures, etc.)
Hojo mutated into various monstrous forms, presumably as a result of injecting or ingesting excessive amounts of his own special Jenova cell-based Psycho Serum.
Jenova cells are also responsible for the enhanced combat abilities of many of the Tsviets and Deepground fighters in Dirge of Cerberus, but probably also contributed to the craziness displayed by many of them.
The Halo series has what are called Waverly Class Augmentors, also known as Rumble Drugs, that have been used by rebels in their attempts to fight Spartans by overriding the body's natural safety limits. Most died well before even getting near a Spartan but not before doing terrible damage to anything in their way. In the short story/animation "The Heart of Midlothian", an AI directs an ODST who was stabbed with an energy sword to inject himself with one so that it will keep him long alive long enough to destroy the ship which has been boarded by the Covenant.
Haze revolves around the Psycho Serum Nectar. One faction uses it; the other faction doesn't and turns out to be being targeted because they have control of land that contains plants that can be used to make Nectar. You play as both in the course of the single-player or cooperative game.
In Jak II: Renegade, one of the ways the Baron tried to recapture his prized experiment, Jak, was by warning him that the Dark Eco in his system, though granting him powerful combat abilities, would eventually drive him insane and soon afterwards kill him horribly. Judging by the previous game's Big Bads, he wasn't exaggerating.
The nightmare drug Valkyr from the first Max Payne was originally meant to be a Super Serum of sorts for the military, enhancing the stamina and morale of infantry troops. Project Valhalla, which was responsible for creating Valkyr, was canceled after the nasty effects of the drug made themselves known. But the key figure of the project, Nicole Horne, knew exactly what she had in her hands and continued the experiment unauthorized. Her bid to silence anyone who caught wind of the project would eventually bring Max Payne to her doorstep when his family was murdered by her test subjects.
Valkyr eventually became a common street drug; with a memorable encounter between Max and Jack Lupino, a gangster driven insane by his "V" addiction. The sequence was either full of terror, Narm, or both. Additionally, Max's nightmare sequences in the first game are a result of being dosed with Valkyr.
Phazon from the Prime trilogy of the Metroid series. It isn't quite clear whether to call it Psycho Serum, radioactive ore, or malevolent fungus.
Project Eden has a drug than grants immunity to pain and increased strength, just one side effect It turns people into acid spitting spiders or crazy mutant dogs, violently and quite quickly
William Birkin from Resident Evil 2 who goes as far to inject himself with his own virus when attacked by a team sent to steal it from him. He massacres them all (except for one, a card-carrying Bad Ass) and goes on to become the game's Big Bad.
Happens several times in Resident Evil 5. About half the bosses jab themselves (or are jabbed by someone else) with a needle full of Uroboros before mutating and trying to kill you.
Terran Marines from Starcraft use stimpacks to boost their damage, with the cost of 10 HP (and Terrans Marines only have 40 HP total) with each dose. It is also stated by the Marine webpage on Starcraft2.com it causes long-term effects not limited to insomnia, weight loss, mania/hypomania, seizures, paranoiac hallucinations, internal hemorrhaging, and cerebral deterioration. There is a character within the Starcraft universe who apparently got addicted to stim packs.
Slightly subverted in that the same web page mentions that Marines almost never live long enough to see these side effects anyway.
In Starcraft II, terrazine gas is a rare variant of vespene gas that stimulates psychic powers, but in its raw form it's highly addictive and lethal — cutting it with jorium crystals makes for a more stable compound that is used to transform Ghost candidates into the Superpowered Prototype Spectres.
Raging Nostrum from Suikoden V is a drug that sends those who take it into an instant Unstoppable Rage with increased power on top of that, but said rage is so extreme that the user loses all rational thought and is reduced to simply screaming at the opponent while going ballistic on them. Oh, and it also kills the user after the effects wear off.
Warcraft have several of these. In the pen-and-paper RPGs optional rules include that all arcane casters are prone to arcane magic addiction which can cause (and not limited to) growing extra limbs (sometimes not functioning limbs as fingers and eyes and horns), paranoia, spontaneous casting (including self teleport while sleeping) and other mental and physical ills. Addiction to demon magic (Fel Magic) is the same only on the highway and with auto-white/green-glowing-eyes (also turns the user to evil in many cases). More literal serum is drinking demon blood (especially Mannaroth's) which turns the drinker into a fighting addict psychopath with uncontrollable urge to kill anything else that has not turn to CHAOS RACE (but mostly orcs). Comes with glowing red eyes, increased size and strength (enough to kill a god with special damage type to accomplish this) and in more sever cases the skin also change color to dark red (also makes the drinker a total traitor and douchebag as an unpleasant extra).
If you're strong enough to "take" it, the Jägerdraught from Girl Genius grants super-strength and near-immortality, but horribly mutates your body. And if you're not, it may kill you outright or mutate your body even more horribly until you beg for death.
And the same probably goes for the battledraught Mamma Gkika gave Gil to save his life (which is labelled "Slightly Better than Death", FYI). At least there isn't any better explanation for Gil's superstrength and other, um, interesting behavior against Dr. Merlot and his clank...
With the use of biomechanical Psycho Serum, wizened Yoda-look alike Colossus Rhodes from Transformers Animated can turn into a giant.
In Transformers Prime the Autobots have created an incomplete synthetic energon, which made Ratchet, tougher, but also more aggressive.
From the original My Little Pony series' second TV special "Escape from Katrina": Witchweed potion. It grants strong magical power (plus a size-boost), but wrecks the true personality of the drinker and is highly addictive. Fortunately, Katrina manages to kick the habit.
In Young Justice, the "shields" Lex Luthor gave to Superboy suppress his human DNA for one hour. He gets the full range of Kryptonian powers, but since the human DNA was used to stabilize Superboy in the first place, Superboy also becomes far more unhinged and aggressive.
Superboy: I get the flight, the heat vision...but I also get angry. Well, angrier.
The memorable Batman Beyond episode The Winning Edge featured the aforementioned super 'roid Venom being mass produced and refined into a nicotine patch-style form colorfully known as "slappers", the hot new street drug for athletes who want a leg up on the competition and gang bangers who need a quick pick me up before a rumble alike. Just watch out for that roid rage.
Truth in Television: At high enough doses, PCP, cocaine, and similar hallucinogens and stimulants grant their users near super-human fighting abilities, because they prevent the users from feeling pain or fear, in addition to making them crazy. This also means the druggies have no way of knowing, or caring, how badly they get hurt, which can have some pretty horrific consequences. Don't do drugs, kids!
This is referenced on Buffy the Vampire Slayer, where cases of vampires going on a rampage are always written off as "thugs on PCP."
Also referenced in City Hunter, where a Psycho Serum is called PCP (the alternative name Angel Dust is more widely used) and has the same exact effects, only with greater strength.
This was also used to rationalise away the first Terminator.
There was a TruTV police car dashboard-cam video (with audio) of a guy on PCP. The wild mood swings were unnerving enough, but the completely inhuman roaring and growling, plus a voice straight out of The Exorcist (when the user was capable of intelligible speech) was serious Nightmare Fuel.
PCP is a dissociative anesthetic, originally marketed as such for surgical use. At sufficiently high doses—which, apparently, isn't much (unlike ketamine, which has similar effects but in a less horrifying manner, usually)—the user completely loses all physical sensation. Think of it as the ultimate Out of Body Experience. Evidently the human mind can't cope with The Void, so it tends to "fill in the blank" with what appear to be surreal alternate realities, or...?
Above info for the purpose of clarification only. Just because they lie about some drugs, don't assume all drugs are relatively harmless. Some of them truly have the ability to mess up your head, permanently.
In the trial for the LAPD officers who beat Rodney King near to death, the officers attempted to justify their actions by claiming that they were afraid that Mr. King was high on PCP and going berserk when he resisted arrest. Turns out that he was actually just really, really drunk, mildly stoned, and just plain tough enough to throw off multiple officers attempting to wrestle him down and to shrug off two taser shocks before the brutal beating commenced.
There's also certain prescription medicines that in already mentally ill (though not psychotic) individuals caused homicidal ideation.
Ephinephrin was used heavily by many insurgents on the Second Battle of Fallujah for this exact purpose; while under the effects of these drugs, their bodies would keep functioning (brains, muscles, and heart activity would continue) even after being injured to the point that they would die from shock, making them sort of like zombie terrorists.
It should be noted that Epinephrine is simply another word for Adrenaline, rather than some strange chemical concoction.
German soldiers used methamphetamines, under names like "tanker's chocolate", in enormous quantities during World War II (over 17 million pills per month during the Battle of France). Many of the German flying aces were on meth, sometimes constantly, and it's widely assumed that the Luftwaffe wouldn't have been able to support the blitzkrieg offensives if their pilots weren't able to fly 12 hours straight thanks to meth. It led to... some side effects after the war. Adolf Hitler himself also became increasingly addicted to the stuff up until his death after it was initially prescribed to him for his constant health problems; it's been speculated that this was responsible for at least some of his erratic decisions during the war.
The somewhat less hazardous dextroamphetamine (normally marketed as Dexedrine) is used for similar purposes by most air forces to this day, under much closer medical supervision. It remains controversial, however, being implicated in at least one friendly fire accident in Afghanistan.
Older than dirt example: alcohol. Used as a psycho serum for its known effect of removing inhibitions, impairing judgement and getting people "pissed angry drunk".