Or you could always constantly remind him of that debt. In every conversation you have with him, no less.
Or to Morte whom you had once pulled from the Pillar of Skulls, and get an in-game opportunity to put him back in exchange for information you can pay for in other (much less evil) ways.
The same can be done to other party members. Including your current love interest.
In fact, the game actually encourages this kind of personal, soul-crushing malevolence over random violence. If you start just killing at random, the Lady of Pain will show up shortly to inform you that you are not top dog in her city, but there is no major penalty for ruining other's lives with just words. Go right ahead!
That is part and parcel of the Clap Your Hands If You Believe nature of the setting. However, Video Game Caring Potential pays far, far better in the game. Kindness to Dakkon, Morte, and company can buff them to Game Breaker status, allow you to use a morphable shape-changing Infinity Plus One weapon, and bolster the status of your allies through hidden mechanics regarding their loyalty. On the other hand, the Entropic Blade isn't that much worse than the Celestial Fire and you obtain it by being a complete monster. Even better example of utter cruelty: Dakkon's people used to be slaves and a huge part of their beliefs center around their escape from that slavery. A certain evil book will empower you with various spells for doing evil acts, including selling a party member into slavery. Hmm. Dakkon, come here a minute, I'd like you to meet someone...
Strangely enough, the most evil and chaotic act in the game is to let Coaxmetal out of his prison tower. Doesn't seem that bad until you remember Coaxmetal is both the best blacksmith in a good chunk of the planes, able to make weapons that can kill the unkillable, and an insane golem that believes the universe's eventual entropic demise should come faster. And you just set him loose upon an unsuspecting Modron population. Chaotic because you just ensured the universe will get a bit of a mauling, and evil because you caused all this destruction in exchange for a nifty weapon.
Rather mild example...in Kingdom Hearts, you can not only run up and smack the Queen of Hearts (who "dies" in one hit) with your Keyblade and she falls in the battle with the card guards, but you can also make Captain Hook's day miserable. You can simply light his pants on fire and cause him to run around in mid-air. Or knock him off the ship and watch as he yells "YOU'LL NOT GET ME OTHER HAND!!!" before he almost hits the water. Even more satisfying when you light his pants on fire andhe puts it out right over the water.
Goofy is also the perfect height for you to throw barrels right into his face.
Captain Hook serves as this again in the boss fight against him as Ventus. If you can get Hook to the edge of the arena you're fighting him on, he'll occasionally try to keep his balance to avoid falling into the water around you both, where the crocodile is currently swimming. If you hit him while he's off balance, he'll fall into the water and take minor damage as the crocodile bites him, causing him to run back onto dry land. However, he'll immediately start swinging his sword wildly shortly after recovering... Hook is also one of a surprisingly high number of bosses in this game who lack Contractual Boss Immunity, so you can freeze him in place with a Stop or Slow spell to inflict even more misery on him without reprisal.
In Kingdom Hearts 3D: Dream Drop Distance, should one of your dream eater allies get KO'd (And you usually have to try to get this to happen, since they're generally Made of Iron), a timer will start ticking down, and if it expires before you revive it, the dream eater will fade away, and leave behind a dream piece. The dream pieces left behind in this fashion can be ones that aren't currently available through other means, meaning you can potentially create some new types of dream eaters much earlier then normal by repeatedly sacrificing other ones (Namely, the ones generated by AR cards, which are easily replaced).
Exploring in Might and Magic 2 you can stumble across a peaceful goblin village... and choose to attack. It was filled with standard goblins, but as many as the game could handle, and with the right spells you could kill them with ease. That's right, you could commit genocide.
When the series went 3-D, it became possible to also annihilate friendly villages as well, including the eventual release of a spell called Armageddon that wiped out everything except your party.
Dark Messiah has the standard "personal" methods of killing things: cutting them up with blades, bludgeoning them with staves, shooting them with arrows, setting them on fire/electrocuting/blowing them up/freezing them solid with spells, stabbing them in the back... and that's before you start exercising the game's specifically designed capacity for creative killings. Almost every single object may be hurled as a weapon (by hand or with the telekinesis spell), that freeze spell can make charging enemies slip and slide... off the cliff, charm spells will make them attack each other, and there are a disturbing number of spiked walls that seem to serve no other purpose aside from being something convenient for kicking enemies into as a change of pace from kicking them off ledges or into bonfires or fireplaces. Of course, since you play the spawn of a demonlord and the game forces you to choose between which of the two love interests you want to kill this is only to be expected.
The Neverwinter Nights module Aribeth's Redemption allows the player to continuously needle Aribeth about Fenthick. And, being the lawful good suicidally depressed Elvish former paladin she is, she sits and takes all of your insults as if she deserves it!
The evil options for every Optional Sexual Encounter in The Bastard of Kosigan. And the evil options for dealing with the prisoners in the Inquisition's basement in Cologne.
As might be expected, Knights of the Old Republic has a number of these if you choose to follow The Dark Side. You can destroy a personal assistance droid on Dantooine in the first game, then tell its distraught owner that it's still out there somewhere so that she'll run into the fields searching for it and get killed by the wolves in the process. Then there is the whole Sandral-Matale feud, which, depending on how you played it could have a happy ending, or, you can let every NPC involved in it kill each other.
The Sandral-Matale sequence may very well be the funniest The Dark Side sequence ever implemented in a video game.
The ultimate example is near the end of the game if you choose to become evil. You get the opportunity to force Zaalbar to kill Mission.
KOTOR is ridiculously, hilariously cruel. On the Sea planet Manaan, you've been asked by a worried father, Shaelas, to find his young daughter. Depending on your actions on the quest, you'll be afforded the option to shake him down for extra credits for his information, before finally telling him "I killed your daughter, Shaelas. And I'll kill you if you tell anyone about this. Now give me those credits!"
It was always impossible to resist the opportunity to play the thorough rogue on Korriban. The final test of the academy would leave the player character alone with the academy master, Uthar, and his assistant, Yuthura. If you suck up to Yuthura enough over the course of the academy's initial tests, she asks for your help in betraying her master during the final test. With him dead, the two of you will share power at the academy. You can accept, and then go rat her out to Uthar, who rewards you by advancing you further through the academy tests and gives you poison to plant on Yuthura, so that she will be weakened during the final tests. The fun part is going back to Yuthura, showing her the poison and telling her what happened. She will chide you for endangering the plan, but give you some poison of her own to use on the headmaster. The really fun part is going ahead and using the poison on both of them, leaving them to come to the slow and horrible realization during the final test that they've been triple crossed. Then you kill them.
The best part about being an absolute monster of a dark sider is how gleefully HK-47 reacts to your cruelty. Get your dark side score high (low?) enough and he'll come right out gushing over you and the number of new ways that the exile has taught him to be cruel. The dark side conversation option is something to the effect of "Stick with me, and you'll learn a few things," to which he replies "Oh yes, Master, I already have."
Hell, let's go crazy. In the sequel, after you defeat Master Atris, you have the option of letting her live. Or killing her. Which, granted, is pretty standard in KOTOR. However, for the sake of sheer cruelty, locking her in a chamber with Sith Holocrons for the rest of her life, letting her go gradually insane is the recommended choice.
Jade Empire.....many of the Closed Fist options are downright cruel, especially the final choice of poisoning the Water Dragon's body with blood from your rebelling companions. The scene is actually a Tear Jerker, as the Water Dragon sadly looks on while you pour the blood into the machine. You then cruelly take her power.
Especially prevalent in later Ultima games: as complexity increased so did the twistedness of clever players. One example that leaps to mind, in Ultima VII one can bake bread. Stay with me here, one of the ingredients is a bucket of water. For some odd reason the game lets you use buckets of blood as well. More twistedness, the first bucket of blood you can find is at a murder site, and the son of the murdered man can join your party. You can, without the game realizing the implications, feed this son bread baked with the blood of his murdered father.
There are entire internet communities devoted to finding out the evil things you can do in Ultima.
In Ultima III you can drum up some quick, easy cash by creating new characters for the party with the express intent of selling all of their equipment. But that's not all! There's a place in a town where you can donate blood (reduction of hit points) and you get payment for it! So before you delete the naked characters you can sell almost all of their blood for cash!
Come across an asari commando who was betrayed by the leader she was devoted to, fed to a giant sentient plant, and out of thanks for freeing her, she gives you the critical Plot Coupon you need to keep going? Nope, sorry, she's too dangerous to let live. Bullet to the brainpan.
There is little that is more satisfying as punching out an annoying reporter. On live galactic television.
That fanboy who you meet in the Citadel? Wants to help you out. Point a gun at him, so he'll piss his pants and run crying. (Surprisingly, this is also one of the correct solutions. Not being cruel enough or not being nice enough when dealing with him will end badly.)
It's probably not considered very cruel, but the game offers you the chance to let Fist live, or murder him as being "too dangerous to be left alive." What probably makes it more cruel is that none of your companions object to his death, and if you bring Wrex with you, you don't even get the choice (since Wrex has a bounty on Fist). Same situation with the warehouse workers who hesitate when you show up.
The renegade Shepard is generally a pretty terrifying person. Apparently pushing people up against walls/sticking guns in their faces is a normal way to end arguments.
A subplot on Noveria involves a Corrupt Corporate Executive even by the standards of the planet, an Internal Affairs agent investigating him, and a Cool Old Guy turian with incriminating evidence against the executive. You could give the evidence to the agent and convince the turian to testify... or you could sell the turian the evidence, then tell the executive about the agent, who then calls her into his office to fire him, and they both kill each other. With Shepard calmly standing right outside waiting for them to finish.
Noveria offers the opportunity for Paragon Cruelty Potential, with an asari representative who asks you to place a spying device on a businessman she's investigating. You can agree to help, tell the businessman what she's planning (so he can feed her false information), then tell the representative what you've done, correctly deducing that her employers are not going to be happy with her. For even more fun, tell her that you've done what she asked and end up getting paid by both of them.
A bunch of innocent colonists have been taken over by a powerful being, and are forced to attack you against your will. You're given a device that can deal with them harmlessly, and their friends beg with you several times not to kill them. Even if you run out of the device (it attaches to your grenades), melee attacks will render them harmless. So of course, the most reasonable course of action is to go in guns blazing and kill every last one of them.
And at every dialogue prompt up to this point, you can choose to tell your team, in essence, "Fuck saving them, that'll take too long. Shoot to kill!"
Mass Effect is one of the only games (at least until3) in which you can casually commit genocide, executing the last Rachni in existence. Who it should be noted was imprisoned, tortured, experimented on, and had her children taken from her and turned irreversibly insane. You have to select the option twice, and one of your squadmates will desperately plead for you not to do it, just to be clear how much of a bastard you have to be to do this.
Mass Effect 2 picks up right where the first game left off in allowing you to be as much of a renegade/bastard as you want to be.
One of your squadmates, Samara, is an Asari justicar who will ask for your help in tracking down a dangerous fugitive who also happens to be her daughter. If you feel that said fugitive doesn't deserve to die for their crimes, no problem! If your paragon or renegade score is high enough, you can choose to kill Samara instead, and the fugitive takes her place on your team.
This video shows what can happen if you pick the absolute worst options throughout the first two games (including, but not limited to, screwing around and letting the captured Normandy crew members die, romancing Liara, who eventually becomes the Shadow Broker and cheating on her with Garrus, alienating the entire Krogan species, killing Samara and letting Morinth take her place, letting Garrus [and most of your other specialists] die on the suicide mission, and letting Zaeed die after the SM by killing him during his loyalty mission). The end result is that the only people left to help you save the galaxy are a computer AI, a pilot and an amoral serial killer who has a tenuous loyalty to you. Almost everyone else is dead. Good going.
Something that was featured in a promotional trailer for the game was the ability to Renegade Interrupt an uncooperative mercenary by pushing him through a window... on the upper floors of a skyscraper.
Mercenary: I've got nothing to say to you. (Renegade Interrupt prompt) If you t- (Shepard steps forward and shoves the man right out the window)'' Mercenary: AAAAAAAAAAAAAAAAAAAAAAAH! Shepard: How about "goodbye".
Downloadable squadmate Zaeed gives you a quest to hunt down a man who double-crossed him. Zaeed sets a fuel refinery on fire in the process, and keeping in mind that dozens of workers are trapped inside, renegade Shepard will reprimand him only by saying, "Hey! The next time you plan on blowing something up, tell me you're going to do it first!"
The fanboy from the first game makes a triumphant return in the second. And instead of pointing a gun at his face, you can actually shoot him. In Shepard's defense, he really was asking for it. (If you think shooting him is a bit harsh, you can also knee him in the crotch.)
You can then stick up for him to the people who were setting him up and lie to him about what a good job he did setting up a really abusive relationship with your fan. Then see below for how you can continue treating him.
That reporter from the first game? You have to opportunity to punch her again. "I've had enough of your disingenuous assertions."
Some players take advantage of Anyone Can Die to kill off characters, despite it obviously being detrimental to do so. If you intentionally choose not to upgrade the Normandy or do any of your crew's side-missions, it is possible to kill everyone in the final mission - including Shepherd him/herself.
Analysis: Defenceless herbivores are no match for guided missiles.
Many of the Loyalty Missions allow Shepard to help the squad work through their emotional baggage... or make it worse. Force Jack to become even more violent and murderous, let Garrus and Zaeed become obsessed with vengeance, deny Kasumi the one thing she has that remains of her lover, deliberately fail Samara's and Thane's missions (which also makes it's impossible for them to be Loyal to you). The Renegade option to Tali's mission, publicly exposing her father's experiments, in particular is incredibly cruel not only on a personal level, leaving Tali absolutely devastated, but also dumps the Migrant Fleet into political chaos and makes it impossible to peacefully resolve the Quarian/Geth war.
Jacob's Loyalty mission ends with confronting the monster responsible for everything that happened there after the crash. You could bring him in to custody, or leave him to face the consequences of his actions. But the most delicious option is to leave him with a half-charged pistol; not enough to defend himself, but enough to give him the option of ending it himself.
Mass Effect 3 makes cruelty a lot less entertaining. The list of people you can kill - you, personally - can include Mordin, shooting him in the back to stop him from curing the genophage; Wrex, after he finds out you sabotaged it; one of Samara's daughters; Legion, if you let the quarians wipe out the geth, in which case you can shoot him four times. Renegade Shepard goes from being an amusing jerk to a monster, and most of the cruelty options also cost you war assets.
That situation where Shepard can heartlessly gun down Samara's daughter? That's only possible if you allow Samara to commit suicide in front of you, which she flat-outs says she only does to ensure her daughter's survival, thus making Samara's death pointless.
In the Leviathan DLC, you find a severed Husk head. You can activate the experiment it's a part of and it sends a powerful electric shock into it, where it screams in pain. Do it enough times (at least the first time you come to the lab) and it will explode.
With the "right" choices and assuming you don't botch the Crucible, you can get at least 7 races wiped out. The Rachni (kill the Queen in the first game, or don't rescue her/her replacement in the third), the Krogan (sabotage the cure, and kill Mordin so he can't try to fix it after the war assuming that's even an option), the hanar and drell (save Jondum Bau over disabling the virus used to deactivate the Kahje homeworld defenses), the Quarians (side with the Geth), the Geth (choose the Destroy option), and the Reapers (again, Destroy, though the Reapers at this point deserve it).
And if you botch the Crucible? Everyone is screwed.
You do get funnier options in the Citadel DLC, when you can blow up the stock at a used skycar dealer's and listen to him yelling "NOOOOO" over the loudspeaker. This doesn't even earn you Renegade points.
Arcanum: Of Steamworks & Magick Obscura offers lots of cruelty options, especially to the talented mystic. One particularly glorious possibility involves charming a wolf or bear, then walking to the nearest town, entering an occupied house, and releasing your control over the wild animal (but not before leaving the house and Magelocking the doors and windows). Other fun activities include using Force Walls and Walls of Fire to trap and burn the clothes off passersby and tricking NPCs into picking up and equipping armor that deals continual poison damage.
If you're really set on playing the game as an evil bastard, one of the required quests becomes to slaughter the entire population of a small, quiet out-of-the-way village. One of the endings you can get even involves you and the Big Bad killing every living thing on the planet.
One of the better tricks I heard about was a friend who pick-pocketed some boots onto the king that made him pass out, then he rigged an explosive trap on the throne then stole back the boots, The king eventually picked himself back up and sat back down on his throne...
Fallout 2 has it even better. The best example would be when you force a conman, at gunpoint, to dig-up a grave where he has buried loot. Half-way through he sheepishly removes a booby-trapped landmine and hands it to you. A popular choice is to wait until he's finished digging, and...
Chosen One: Hey Lloyd! CATCH!
In Modoc, you can persuade a guy to cut off his finger as a way of settling a deal. You can, of course, change your mind about taking part in the deal afterwards. "Now, take your finger and saute it in a light garlic sauce. Very tasty dish!" The guy in question doesn't react well to your prank and, after bandaging his hand, attacks you.
Broken Hills, leading a midget down a well, and then leaving them down there with the...things.
Just helping the anti-mutant guys in Broken Hills condemns their settlement and all its occupants. Turns out the humans can't survive so well on their own...
You can destroy the nuclear reactor in a peaceful Ghoul settlement, destroying the lives of dozens of peaceful mutants and poisoning the water of a nearby city forcing them to become refugees.
Annoyed by all those kids who pickpocket you? Get revenge by arming the explosives in your inventory, then reverse-stealing them into their inventory.
One must be careful with pickpockets and explosives. The pickpocketing children immediately try to fence anything they steal to nearby merchants, and explosive timers don't count down while in merchant inventories. The game, however, does remember the timer's state—-buying the explosives back from the merchant will lead to a bit of a surprise.
The game specifically gives you the option to aim your weapon at the victim's crotch. In the very first village of Fallout 1, within 5 minutes of starting a new game, you can smash a young child in the nuts with a sledgehammer. Alternately, you could go back to that raider who used to kick your ass, and introduce his groin to your brand new powerfist.
Seducing a hillbilly son or daughter results in a shotgun marriage, unless you're a smooth talker. This hillbilly husband/wife will be entirely useless, and cannot be removed from the party. You can get a quickie divorce in New Reno...or you can sell them into slavery instead for a quick buck.
Or, you can rent them out to a porn studio as a "fluffer" for three bottlecaps.
You can also get back to Grisham and tell him that his son/daughter disappeared if you had a divorce or sold him/her to slavery. A heart attack will kill him.
You can feed your spouse into a hacked organ extractor (it can remove bowels) but this isn't quite so cruel.
Selling party members to slavers not enough for you? Join the slavers yourself and help enslave tribal savages. The fact that you're a tribal yourself won't bother boss Metzger, though the other tribals will be.... less than happy about your new career.
Give Cassidy some Jet. Order him to shoot up. Watch him have a literal heart attack. When he told you his ticker wasn't so good, he wasn't kidding.
Murder nearly every living creature in the game, be they man, woman, child, friendly, hostile, or unawares. There is nothing stopping you.
In the first game you actually can murder every single living thing in the game, including the usually-invincible Overseer if you finish the game with a low enough Karma Meter.
There were special ways you could sneakily assassinate the heads of the crime families in New Reno - some rather sadistic. To whit: re-arm Bishop's safe with explosives, then change the combination. BOOM. Give one of the youngest Wright kids a loaded gun, which results in him shooting his own dad. Give Big Jesus Mordino any kind of chem, even a Nuka-Cola, and watch him suffer a heart attack. Steal Mr Salvatore's oxygen tank, then enjoy the floating text as he slowly, so slowly, chokes to death.
Not to mention you probably got the combination to Bishop's safe by sleeping with his wife. You can also sleep with his daughter, and if you're a man and don't have a condom in your inventory, she'll get pregnant. Yep, you can literally screw that family over.
Though your offspring does do well in New Reno, as one of the ending voiceovers will tell you.
Some of the death animations when killing foes were pure Squee! as well. How about turning the foe's insides into bloody gibbage with burst fire, blowing a football-sized hole in their gut with a single bullet, slicing them apart with laser, melting them into a puddle of goo with plasma, or crisp them with electricity - turn 'em into a neat pile of ash. And, of course, the flamer... set 'em on fire, watch them run around in flames before collapsing. Lovely.
In Fallout 3, you can walk out of the Vault, and arm a nuclear bomb in the middle of a major quest hub within five minutes. And get paid, well, for doing so. Big boom.
In a later mission, the leader of a "Matrix"-style simulation of 1950's Americana has gone nuts and begun torturing the other residents. The player is given the choice to help torture them or mercy-kill them.
You can't kill children. The game won't stop you from, say, laughing at a kid you just orphaned, or sentencing another kid to certain death, abandoned and the only human in an entire town in the Wasteland.
Unless you use this mod, which makes them killable.
In early versions of the game, you could actually, with the help of a perk called "Mr. Sandman," slit the throats of sleeping children. And they'd live, due to being unkillable. This Good Bad Bug even led to a method of gaining infinite XP, until it was (sadly) patched out. Children are now unkillable even with this perk...unless you use the mod above.
It can be done in Fallout 1 and 2, and you'll even get a perk for it. The perk makes people hate you. Hooray!
Not only can you kill children in the first two games, but they have a full suite of death animations. Shooting a child with a flamethrower will cause the poor mite to run around screaming and burning until collapsing into a pile of ash. This was considered sufficiently gruesome that European versions of the game had to be patched to remove children entirely. Unfortunately, this was accomplished by simply rendering them invisible, breaking several quests and rendering the source of their floating dialogue inexplicable, as well as infuriatingly not stopping them from pickpocketing you. Ironically, these heard-but-not-seen children could still be killed by stray gunfire.
Worst of all, there's the Child at Heart Perk, which makes children trust you more easily. If you don't want to be a horrid villain, this makes it easier to protect children, but if you do, it makes kidnapping children for slavers easier...
You can find, and turn in to be enslaved or destroyed, a synthetic human who intentionally had his mind wiped. If you do things right, he'll even beg. And you get a Perk for doing so.
Even better, you can get the perk AND a sweet, unique gun: Tell Harkness that they are an android, then tell him you'll kill Dr. Zimmer yourself, as otherwise you won't get the perk. You'll get his unique gun, as well as Good Karma. Next, tell Dr. Zimmer that Harkness is the android, and you'll get his perk and Bad Karma, neutralizing the Karma gain from earlier. Now laugh evilly as they wipe his memory and take him away. You could also kill Zimmer and his Bodyguard, but that's not nearly as cruel.
You can do the tutorial just beating the ever-living crap out of everyone. The funniest bit? After getting the BB gun the Kid keeps shooting daddy, who passes out just when the celebratory picture is taken.
There is an achievement for sticking a live grenade in someone's pocket and the game keeps track of how many times you do it with the "Pants Exploded" stat.
You can can use the fast travel system for some extreme sadism. Get the Experimental MIRV (a nuclear catapult that fires 8 mini nukes shotgun style), go to the center of Megaton and fire straight up. Fast travel to Megaton and you'll be right outside the town. Wait a few seconds and walk in. The only living thing in that area is you.
You can take a perk allowing you to become a cannibal. Enough said.
Or have Angela seduce Diego, then massacre the wedding party.
Even worse than the above examples is using the Enclave's Kill Sat to blow up the Citadel, permanently betraying the Brotherhood and turning them hostile.
Kidnapping an innocent female NPC with the Mesmetron and a slave collar so you can sell her to the slavers not cruel enough for you? If you have Lingerie, give it to her, and she'll change into it.
In Fallout: New Vegas, a child will ask you to look for their lost teddy bear, Mr. Cuddles. You can find the toy, sell it to a trader for a few caps, and then go back to the child and tell them that Mr. Cuddles is dead. Evil in its most basic form.
For more teddy bear fun times, there's a child slave at the Legion encampment who also asks for help getting her bear back. You can tear Sergeant Teddy in half in front of her.
Oh, that's just the tip of the iceberg. You can sell one of your companions into slavery, kill a man and cook him into a meal before feeding his remains to his former colleagues, crucify a man, reprogram HELIOS One resulting in the slaughter of everyone there, blow up the Brotherhood of Steel bunker before Veronica's eyes, and much more.
New Vegas is the only one that offers you the chance to sell your companion to cannibals because they were short a main course.
You can exact revenge on the Legion for releasing a dirty bomb in an NCR held town by doing the same thing to their encampment nearby, killing everyone there including a family of slaves.
For consequence-free cruelty, you can attack Yes Man, whose submissive nature means that all he's able to do in response is to beg for mercy and talk about how much he deserves it. Of course, since he's an A.I., he can freely upload himself to any Securitron. Rinse and repeat.
There's one Legion quest that involves blowing up the NCR's monorail into New Vegas, then framing an innocent soldier so the Legion Double Agent can continue to operate in secret. One of the methods of killing the soldier, after planting evidence in his room? - distracting him with talk of a great prank you've cooked up, as you pull the pin out of one of his grenades.
The Dead Money add-on allows you the option of talking Dog into killing himself by breaking his own neck with a length of chain.
Lonesome Road has a bunch. Whenever ED-E plays his recordings for you, you have the option to tell him that you don't give a damn about his problems, that he is only a tool for you, insult Whitley (who is basically his father), and threaten to kill him. There is no punishment for this. At the end of the DLC you can nuke the Legion and NCR
A mild example: There are 13 potential companions, and if you max out their Relationship Values, you get a permanent perk. Some can also be romanced. So what do you do with your new BFF? Immediately drop them in favour of someone else, of course, so you can get their perk! For extra "fun", keep all your exes hanging around your home base, so that they will keep on seeing each other, and see you with your new squeeze.
Similar to Fallout 3, you're able to sell a Ghoul child into slavery or murder his parents in front of him.
You're able to withhold the cure for a deadly disease from a dying child simply because you don't want to deal with the small health penalty.
Fallout's spiritual predecessor Wasteland allows you to attack some kids who laugh at you. As you kill them, more kids will appear and the atmosphere will get more and more creepy, ending with a puppy crawling into a dead child's arms and the camp suddenly looking as though it had been abandoned for years.
In Morrowind, it's possible, with sufficient skill (or judicious use of cheat codes) to make a spell that will paralyze an enemy for extremely long periods of time and do 1 point of damage per second until they die. You can then sit and watch as your enemy is slowly burned/electrocuted/poisoned/drained of life. With some of the alchemy exploits, this can also be done using poisons. Do this with drain life and multiple victims, and you have a self sustaining means of continuous health regen while in a dungeon. This would mean that you are being sustained by the continuous suffering of your foes. Add a continuous health regenerating effect, and it's possible your enemies will survive this torture, so that you can do this over and over again. You can make this last in-game months, or years. Add soul trap, and death will only change their fate from agony to bondage within a soul gem. Molag Bal would be proud.
All non-plot-important NPCs in Oblivion can be killed, making it possible to go on killing sprees of hundreds of individual characters. Plot-important characters can only be temporarily knocked unconscious.
But why just kill people yourself when you can get them to kill each other? The Frenzy effect causes the target to go berserk and attack the nearest person. Because it doesn't count as an attack, you can use it in the presence of guards without committing a crime. Riots are fun. You can start a Guard vs. Townsperson brawl that can result in every non-essential NPC in the town being ruthlessly slaughtered by the very guards that are supposed to defend them.
To add to the hilarity, drop some weapons on the ground (whatever kind you want) then cast the Frenzy spell. All affected NPCs will run over, pick up a weapon (if they don't already have one) and then go bat-shit on the closest person, friend or foe. Made even more hilarious on the PC version where there is actually a spell (added through a mod) that can both give and revoke essential status to ANY NPC. Yes, it is as hilarious as it sounds having a literally unkillable begger armed with with an enchanted Daedric longsword go on a murderous rampage. And the Grey Fox wants to help those little bastards too...
Poisoned Apples (which you get in the Assassins Guild quests) are a good source of fun. If you see an NPC sit down and eat, just put one on his plate. Ten seconds after they eat it and their poor, lifeless, limp body will be hanging from the chair.
Create a weak, but long-duration Destruction spell, say, 3 HP/Sec fire damage for 120 seconds. To the NPCs, that's a full hour of being on fire. Be sure to call this spell "Hell".
In the Shivering Isles expansion to Oblivion, part of the main quest requires you to reactivate a dungeon used to "greet" newcomers to the Isles. After you reactivate it, you see a group of adventurers come into the dungeon and enter 3 rooms. In each of these rooms, you get to hit one of two buttons to decide on the adventurers' fates. One of the buttons will brutally get them killed, while the other drives them insane.
Similarly, in the main game, there's one section of the torture caverns in Camoran's Paradise featuring an immortal in a cage hanging over a river of lava. There's a lever on the ground beside him. If you pull it, it dunks the cage and rises up another. Have fun.
Let's hack now shall we? Hack Hand-to-hand and adjust it to a disgustingly high level...now taunt someone into attacking us. BLAM!!! Knocked out for three days straight. Three days later....they get up, remember that you insulted their mother and then come after you again. POW! Three days later...BLAM!!!!
In a similar way to the hand to hand example above, custom fatigue draining spells can be added to zero weight items, which when reverse pickpocketed into the inventory of essential characters leave them paralyzed and unable to die.
Good fun can be had with demoralize (fear) spells, causing NPCs to run around in panic.
Skyrim continues the tradition, adding shouts into the mix. Much fun can be had with Unrelenting Force, which lets you knock others a few feet into the air by yelling at them. You can shout others off a mountain, and spend a few minutes climbing down just to see how far they fell, or shout them into a river and watch them get swept away and into a waterfall.
Skyrim also has randomly activated finishers, all of which are quite brutal, the most prominent of which is cutting off a person's head. In order to get the player to take care of spouses and followers none of them are coded as unkillable. Some players realized the implications.
Is an NPC given invulnerability owing to their "essential" status? No problem. Just flog them repeatedly, so you can train up your weaponry skills. Taken Up to Eleven with Ancano or Elenwen; in the College in Winterhold, it's possible to beat him to within an inch of his life with nobody interjecting, and your followers will help you regardless of morality level, with the latter you can Fus Ro Dah her off a cliff so she has a painfully high fall. She'll still survive, but it's something.
Those Civil War quests are boring, boring, boring? Well, you can remind those Bethesda morons what medieval warfare is supposed to be like, and spice up your walkthrough with a little sack, pillage and burn! Right after a camp commander orders you to attack a fort, don't go there immediately, but rather take your most crime-friendly companion (or better, install a multiple companions mod and gather a whole squad of Bloody Mummers) and harass the hold in which your target fort is! Hack everyone you meet on the road to bloody bits, plunder Khajiiti caravans, raid shops and warehouses in cities and towns, and kill, kill, kill guards! Lather, rinse, repeat until you take everything not bolted down and slaughter anyone who resists (accruing an astronomical bounty), THEN head to the fort and capture it. The Jarl of the hold will change, and your bounty will be cleared. Repeat with the next fort. Don't forget to install a driveable wagon mod; you'll need the wagon for all that loot.
For bonus points, complete "A Season Unending" and give up some of your friendly holds to the enemy, then sack them as described above and retake them.
For those who played Skyrim on consoles, you can kill essential characters by repeatedly casting any "reviving undead" spells such as Dread Zombie. Their bodies will turn into ash piles and marked as dead. Beware that some important quests rely heavily on their presence. So be sure to finish all of their quests before killing them.
You can also do some good with your cruelty. Before starting the Dark Brotherhood questline, acquire a Black Soul Gem. Kill Grelod the Kind and Soul Trap her in the gem. Then adopt one of the children from the orphanage, use Grelod's soul to enchant a dagger, and give it to the kid as a present.
During the questline, you're sent to murder the Emperor's cousin at her wedding in Solitude, and you'll get a bonus if you do so while she's addressing her people on the balcony above the court. If you just want to get the job done, you can kill her with a bow you own or with the enchanted bow provided on another balcony. Alternatively, you can get creative and crush her with a gargoyle precariously perched above her, or, for the REALLY evil, you can reverse-pickpocket a suitably powerful weapon and a Frenzy poison onto the groom and let him do the job for you.
Hearthfire adds a comparatively minor one: You can end up with steward, spouse, housecarl and 2 kids for your house. Building enough beds for all of them is optional.
Any of the rape mods (yes, there is more than one) that makes the characters strip and do the nasty when a foe surrenders.
Fable allows you to slaughter practically every single person in the game, save for the first city (the laws prevent you from pulling out your weapon, but you can still pound away at innocents with your fists until they're unconscious), and if you're in a city, all you get as punishment is a high fine and a banishment from the area for a couple of in-game hours. In fact, in order to get one of the best weapons in the game, you need to sacrifice an innocent to an evil god at a certain time of night.
Best Level-up ever, or worst, uses this very mechanic in the first town. While the town proper does not permit weapons or even the mechanics behind them to work, it also makes the people unkillable. Thus, as soon as you enter the town for the first time, you can gain a huge in-game advantage through something referred to as the "Ike Turner Strategy." Step one: seduce a woman in that town (the men fight back, and can interrupt the chain). Step two: have her follow you to the adjacent area of docks, which is still part of the city so weapons are not permitted, but combat targeting and throwing punches are thanks to the boxing event. Step three: corner your immortal girlfriend in the warehouse via clever placement of crates, target her, and start swinging. Step five: pass the time. Change the TV to a movie, (maybe J-Lo's "Enough" to reduce karmic backlash) while holding the remote and tapping the attack button. In less than the two hours it would take to finish the movie, the physical XP earned (most notably from the CHAIN of successful hits) will be enough to MAX physical stats on a starting character. The only penalty is a similarly-maxxed out evil meter, fixable if you care to do so by killing bandits or just donating money to charity. The countless stories of spousal abuse buy-offs makes this a particularly ghoulish commentary within the game...
But why stop at killing? The game also lets you be an evil jerkass with business sense by permitting you to slaughter an entire village, buy up all the newly vacated property, and lease it to new tenants for cash. Murder for profit in the most literal sense.
It is indeed possible to kill people in Bowerstone, the city with the weapon prohibition. All you need to do is get the guards shooting at you with their crossbows and wait for some unfortunate collateral damage...
Why wait for the guards to do the dirty work when you can hire an armed mercenary who's inside the same city who is more than capable of killing NPCs?
Fable II takes this kind of thinking mans violence to new heights. The game has a semirealistic economy that functions as a result of how people are feeling. In short? Rampage through town to sink the economy, buy up all the property and jack the rent up to sink it lower AND make money faster, and then buy goods off your abused tenants at a hilariously low price!
In Fable II, there's the Wheel Of Misfortune, which kills the sacrifice in a number of ways. There's one non-fatal fate: the victim is transformed into the opposite gender. (Which is, of course, hilarious.) As well, to get a special weapon that deals damage to "good" creatures, you need to sacrifice a spouse.
The best thing about killing your wives for a legendary weapon had to be the good points you got from doing it. Marrying a girl gives you 100 good points, x renown, and x money as dowry. Having a child with said girl gives you 50 good points. Sacrificing your wife for power gives you 100 evil points(-100 good points) and a small amount of corruption points plus money and with enough sacrifices the legendary weapon. You have a net gain of 50 good points for marrying, impregnating and then murdering a random girl.
As well, you can also sell people into slavery, rob stores, extort civilians for money, abuse spouses and your dog, carry out assassinations for quick cash and help drive at least one person to commit suicide.
Fable II also introduced subtargeting to the series. Yes, shooting people in the crotch or BLASTING THEIR HEADS CLEAN OFF THEIR SHOULDERS are perfectly viable tactics.
Try killing all the adults in a town, then buying back the children's affections with gifts. They don't care if you murder their parents in cold blood, if you give them toys, they will love you.
The underrated tactical superhero RPG Freedom Force practically LIVES by this trope. Every building, vehicle, tree, NPC, etc. is damageable & destroyable. This is somewhat balanced by the fact that you lose experience (or "prestige") if you cause too much damage and certain levels require you to protect specific landmarks, but that doesn't make whittling down an apartment building to near-death, then punching a civillian into it from two blocks away, therefore causing the entire thing to collapse any less hilarious.
Contact allows you to kill and attack just about everything you come across, from civilians to hapless livestock. You'll lose karma, though.
In Soul Nomad & the World Eaters, the game allows, and sometimes even encourages, you to do things to the various NPCs in towns and villages, such as stealing from them, beating them up, kicking them in the face, or forcibly conscripting them into your army. This is all menu-based, meaning the game is basically suggesting to kick people for no good reason. And let's not get into the Demon path, which basically calls you a wuss for all that.
In the Paper Mario games, there's the Whacka, an absolutely adorable little guy and a member of an endangered species. If you hit him with your hammer, you get the Whacka's Bump, which is a fantastic healing item. Go back and do it enough times, and you'll eventually have killed the last Whacka, you freak.
And then there's that toad in the station that talks about the cute little Whacka and how she wants to protect it or something. Little does she know that you plan on killing it! Once Whacka's dead, she still won't even know what just happened, and comment on how she hasn't seen him in a while, clueless the whole time that his last remains are now part of a delicious meal. Oh, and he'll explode in the first game like a defeated enemy, and even drop a few coins or even flowers (if drop-rate increasing badges are equipped).
The game literally asks you: "How do you sleep at night?" However, you need at least two of them to get 100% Completion.
Much later in the game, A few scenes will happen where, after using a companion's skill, several copies of them will appear all claiming to be the real one. Hitting the real one by accident would be understandable(at which point the remaining Doppelgangers attack). However, with Kooper, rather than bringing back some duplicates, is surrounded by very poorly disguised monsters. You can still hit Kooper, though, and he'll call you out on it.
In Super Paper Mario, if the player talks to Whacka, he'll remark that he doesn't think anything can ruin the nice day. That's before Mario showed up with his hammer. It's made worse after he dies: his Cragnon friend comes looking for him, and gets pretty depressed when she finds out he's gone. Tippi says the girl's heart is about to burst.
Try talking to him after you've hit him a few times. With each whack, he gets steadily more incoherent and confused...So even if you don't outright kill the poor thing, you've probably given him irreversible brain damage. Is 100% Completion really worth the cost of your soul? Especially since you don't actually get anything for it?
Well not exactly the LAST one. Only in the Paper Mario series. In Mario Party 6 about a million of them appear on the snowflake board.
In Paper Mario: The Thousand-Year Door you can push your partners into water or even spikes; and the best part is that they don't lose any HP from it, unlike when Mario falls into them.
Also in Paper Mario: The Thousand-Year Door, after beating Doopliss for the first time, he steals Mario's identity, and your partners follow the fake Mario, leaving you alone as a mere shadow. When you fight Doopliss at the end of the chapter, your partners are helping him and attacking you. You must defeat Doopliss, but you can also attack and beat your four partners.
In Mario & Luigi: Superstar Saga, it's possible to convert Luigi's HP to money as soon as you get the Hammer techniques. With Mario on front, have Luigi hit him with the hammer. Now try to do a High Jump. While Luigi is doing the High Jump, have Mario jump. Luigi jumps back in shock, he loses 1 HP, and you get 1 coin. Great way to grind for coins. You can keep doing this as long as you want until Luigi is left with 1 HP. Even then, you can just use a few of your 30+ Mushrooms on your inventory to recover Luigi's HP... only to have Mario hit him in the crotch again.
Before you get the Hammer or Hand techniques, it is still possible for the brother in the back to hit the one in the front with these moves. Luigi/Mario will then look back in anger. It's tons of fun to do, and you don't even lose HP for doing that.
After completing the game, you can go back to Week 2 and use the Rhyme Pin to attack Reaper Beat. It's funny because they're siblings who love each other. It's impractical to do, but still.
In Valkyria Chronicles, you can either let your troopers rush towards the enemy for a suicidal (and admittedly, stupid) move, or sock a rocket right in the enemy's face. Your choice.
Ramming people with tanks does nothing but punt them around like a rag doll and make them scream in agony. If you want to be outright cruel to a mook? Stock up 20 CP and spend them all to just ram a poor guy into a wall with the Edelweiss. He won't die, and likely will be stuck there for him to die by your gatling gun on his turn. Oddly enough, the "ran-over by tank does zero damage" thing applies to enemy tanks, so if you want to be mean without losing troops... get your redshirts ran over by the Batomys.
Trapt, a game which consists of setting a complex series of traps to kill enemies. Said traps are rather cruel, especially 'Dark Illusions', environmental traps which require a bit of set-up, which can, for example send someone through the clockwork of a music box, complete with bone crunching sounds.
All of the Deception games, really. Skewering young girls on deadly wall spikes is pretty common... especially since then you can harvesttheir bodies.
You can complete the Bakumatsu (Ninja) Chapter of Live A Live by either doing a Pacifist Run and avoiding unnecessary kills (I.E everyone except the undead creatures and monsters you encounter. Bosses fall into said categories) or becoming death incarnate and murdering every NPC in the level, including women and harmless merchants. Either way will reward you with a powerful weapon for you to use in the final chapter.
Avernum. If you register, you can up your army until they are super powerful...and cheerfully wipe out the majority of the towns if you so desire. Even the super powerful guards cannot stop you! You can also set the days far in advance and not bother killing off the plagues of monsters. Townies will DIE if you do this! Having her husband killed by monsters makes the blacksmith lady very sad.
This is also doable earlier on with a highly skilled mage/cleric team combo. The mage summons monsters that do chip damage to guards, meanwhile the cleric continually summons higher level shades as meatshields and mobile obstacles. Made even simpler in the sequels due to simulacrum.
Boy: YEEEAARRRGGGGHHHHH! * Goes Ax-Crazy and repeatedly slashes the townsperson until he vanishes and dies*
Citizen's death quote: Hello young man! Welcome to Topple!
Final Fantasy VI features a sequence where you can save Cid by catching fish. Fail the fishing minigame, and he dies. However, many players fail the minigame on purpose - partly because of this trope, partly because it's an annoying minigame, and partly because Cid's death is generally considered to be one of the most tragic moments in the game.
Final Fantasy VII has one part where you can be a total asshat to Red XIII. When the party reaches the beach town from Junon for the first time, Red XIII sits in the shade and notices how his tail loves to bat the soccer ball the kids are playing with. You can smash the ball to Red XIII and hit him in the face, causing him to growl, but that is it. Best part is you can do this endlessly and Red XIII won't be mad at you later.
There is another part in the game where you get to be cruel and it's a part of the storyline! Around disc 3, after Tifa manages to escape from Shinra, Scarlett confronts Tifa and slaps her in the face. You then get to press O and slap Scarlett back over and over again until she gives up. Safe to assume that at least a few people made a separate save file just so they can go back and play the slapping mini game.
When you first visit the Sector 5 Slums, there's a kid talking in his sleep about his treasure in the drawer. If you open it, you get his 5 gil. When you return after the destruction of Sector 7, you can see him crying about it. However, if you leave it alone, he saves up and buys you a Turbo Ether.
On Disc 2, when you go to get the submarine, there are two Shinra grunts and their superior inside. These are the guys Cloud met on Disc 1 while posing as a grunt himself, and as such, you can either take them prisoner... or just kill 'em dead.
There is a bird's nest in North Corel with a mother cockatrice and her chicks. You can choose to leave it alone or go for a treasure, but are strongly encouraged to leave it alone if either Tifa or Aeris are in your party. If you choose to go for it, the reward is ten Phoenix Downs, but first you have to kill the mother cockatrice. And the girls will make fun of Cloud's hair.
In Final Fantasy Crystal Chronicles: The Crystal Bearers you have the ability to manipulate gravity. You use this power to toss monsters into one another and make impossible jumps. You can also use it to toss random civilians around. Some of them drop money when thrown. Old ladies are the most likely to drop Gil. It's like they want you to abuse your powers.
They do: There are achievements for getting an old lady who comes only when you've thrown a lot of them around, and one for throwing guards about and getting sent to prison.
One of the Knights of Pluto wants to quit the Alexandrian army to become a writer, and asks Steiner if he can leave the Knights. Steiner can either say that he'll eventually let the knight leave, but first he has to find Princess Garnet, or he can be a Jerkass and yell at the knight, telling him he can't leave before basically telling him to get off his lazy behind and find the princess. Either way, the poor knight runs off in tears.
Final Fantasy X: The wonderful Thunder Plains, which are constantly plagued by thunder and lightning. You can take shelter near very tall pillars designed to divert the lightning, jump out of the way of a strike with good timing, or - if you're feeling particularly sadistic - let Tidus get struck by lightning. over and over again. For as long as you want. (Unfortunately, this feature was removed in Final Fantasy X-2.)
Speaking of thunder... You know Rikku - the Genki GirlWrench Wench who has a Fear of Thunder? Because of how targeting works in this game, you can cast lightning-elemental spells on her endlessly (as long as she has HP to burn) to see how she reacts. Go ahead, try it... You Monster.
There's also a scene where the rest of the Party tries to leave Rikku behind in the Thunder Plains. By using the Circle button to walk, the Player can join in on ditching her.
Final Fantasy XII: There is only one enemy in the game that will not attack you on sight: A Garif hunter, who is walking around on the plains near his hometown, hunting animals for food. You have to kill him to fill out your bestiary. Multiple times. He also stands no chance against your party of mighty godslayers.
E.V.O.: Search for Eden has a point in the second chapter where you are actually able to kill and devour a pair of helpful amphibians (one of whom is a child whose father sacrificed himself to save his species). Doing so causes a horrified Gaia to ask what you're doing. If you eat the meat the two provide, you're instantly killed. (That's karma for you.) You can avoid dying, though, by eating one and immediately evolving in some way, restoring your HP to full.
Playing Might and Magic 6? Going for Master Dark Magic? Head to Free Haven and cast Armageddon. Instant evil party~! Just make sure you hotfoot it to Paradise Valley before going to a castle...
In Might and Magic 7, it's quite easy to bait a pack of monsters into a town and watch them slaughter the helpless peasants. Not only that, but in the tutorial mission you get rewarded for doing this. Normally, you have to buy a lute for 500 gold and you can accept a magic wand in exchange for performing a later favor for the mercenary guild. Get the NPCs who offer these two things killed by monsters and you can loot the items from their corpses.
In Pokémon HeartGold and SoulSilver, a random NPC in Cianwood City says that your rival scared him into giving away a rare Pokémon. He then gives you another, a Shuckle, to keep safe. You're free to do whatever you want with his Pokémon, use it in battle, breed it, even release it. To add to it, if you talk to him again later in the game, he'll say that he thinks it's OK for him to have his Pokémon again, but if you don't give it back, he'll tell you that what you're doing is basically stealing, making you no better than your rival. However, he will let you keep it if it has high friendship/happiness.
In the same games, you have your lead Pokémon walk behind you and follow you wherever you go, including places they would naturally never want to be, which leaves the door open to some Poke the Poodle. Such as splashing in puddles with a fire Pokémon. "Quilava looks angry!"
The happiness system. There are most of the time only things that increase a Mon's happiness, which result in them evolving; on the other hand, you can also decrease their happiness by letting them faint in battle and giving them bitter medicine. Especially seducing with the Revival Herb, it resurrects your fainted Mon with full health. Besides the Max Revive (which only exists in limited quantities), it's the only item with this power.
The move Frustration becomes more effective the more your Mon hates you. Taken to unfunny levels in Pokémon Black 2 and White 2 with Ghetsis' Hydreigon, who has that move, at really high power too...
Consequences of the (un)happiness stat have no impact on anything, really. The only exceptions are HeartGold and SoulSilver, where you could speak to your Mon and it would display a speech bubble, sometimes with an unhappy face.
PokéPark Wii: You can dash Pikachu into smaller mons and send them flying a few feet into the air. Most times out of ten, the victimized Poké will cry its little eyes out if it's one of the adorable ones. However, it's also averted with some. Dash or Shock a Pokémon like Scyther, and they will knock six bells out of Pikachu!
The 5th generation of Pokémon introduced Audino, a pseudo-replacement for Chansey. They're these adorable little pink, rabbity critters that can be encountered in nearly every patch of grass in the game under the right conditions. They also have an insanely high experience yield. Perfect for grinding, right? YouMonster.
In Pokémon Snap, you can use Pokémon Food and Pester Balls to stun and/or drive Pokémon out of their hiding spots, just so you can take their picture. Taken to an extreme in Rainbow Cloud, where, in order to get a good shot of Mew, you need to nail it with dozens upon dozens of Pester Balls in a row, so that it stays stunned long enough for you to get a nice close-up picture.
This gets worse with the Electrode in the Power Plant, which will explode when hit. You're basically forcing the constantly smiling Pokémon into hurting themselves for no reason.
While the Pokémon-Amie feature in Pokémon X and Y allows for plenty of Video Game Caring Potential by letting you feed and pet your Pokémon, it also lets you do things to upset them, such as petting them in a spot they dislike, hitting them, or dropping their food on the ground (Which provokes certain species even more then usual if they're hungry). You won't be punished for doing it in any way, either.
Vampire: The Masquerade – Bloodlines makes it very possible to have a bloody rampage, slicing hobos to bits with a fire axe, snapping the necks of club kids, and eating hookers for a late night snack, but discourages this in two ways. One, killing innocents (as in, anyone not trying to kill you,) even when feeding reduces your Humanity, the game's Karma Meter. Having a low Humanity makes you more likely to frenzy, where you lose control of your character and try to drain any nearby juicebags dry. Also, any use of obvious supernatural powers or feeding when people are watching results in a Masquerade Violation, which results in Vampire Hunters following you around. Also, if your Humanity drops to zero, or you stack up five Masquerade Violations, it's an instant game over. However, there are limited opportunities to regain both Humanity and redeem your Masquerade Violations, so you can get away with this to a point. Plus there are enough opportunities for plot assisted cruelty as well: sending a hapless TV Show Host to be devoured by a flesh-eating Vampire, enticing a naive thin blood to attempt to assassinate the president, and arranging for a young woman to have her blood slowly drained and sold to local Kindred are just a few of them. All of these do cause your Humanity to drop though, so it's a fine line.
However, with the judicious application of console commands (namely vstats get humanity 10 and debug_change_masquerade_level -1), you can keep your Humanity and Masquerade Violations at non-game-ending levels as long as you want, allowing you to terrorize the good morsels—erm, citizens—of the greater Los Angeles area to your little black heart's content.
Also, in one of the missions, you're supposed to rescue a kidnapped person in a spa/brothel. Once done, this room becomes a free zone for killing, feeding, doing whatever you want. It's a bug, but fucking awesome!
It's also worth mentioning a few of the clan-based vampire abilities, such as forcing the target (or targets) to commit suicide, attack their allies, get eaten by a swarm of insects, or have their blood boiled while they are alive. Have fun splattering the walls with blood and organs.
.hack//G.U. gives you Chim Chims, whose only purpose of existence is to get kicked by the players and have their cores used to open some doors in the dungeons. It doesn't stop there... Now try to run into those little critters with your steam bike. The game even rewards you for it!
And don't forget the Lucky Animals. They can be even cuter than the Chim Chims. And you're rewarded for kicking/running over them by the Lucky Animals themselves giving you special bonuses for being fast enough to kick them, such as item sets, money, temporarily increased stats, and a few saves from game over. Kicking the Unlucky Animals doesn't really give you any bonuses; it just rids you of any negative effects they give you if you don't.
It's worth noting however that most of the Lucky Animals are actually happy for you if you can manage to kick them.
Hell, there's a sidequest to kick all the lucky and unlucky animals, for which you get even more rewards. Same with kicking as many Chim Chims as possible. Kick the Dog in its most literal sense.
In Dragon Age: Origins you can do quite some cruel things such as slitting the throat of a kid instead of going into the kid;s dream and help him to get rid of the demon possessing him.
That is not even close to touching how much of a psycho you can act in that game. You can go into the kid's dream like you're supposed to and instead sell his soul to the demon. You can convince werewolves to slaughter a village of elves, desecrate religious artifacts, bait your party members into attacking you (they die of course), toy with the affections of your followers, allow a crazed woman to get her hands on a superweapon, backstab people both literally and figuratively, and generally act like the biggest asshole in all of Ferelden.
One particularly nasty possibility is romancing Alistair as a female PC, then sparing Loghain at the Landsmeet and having Alistair executed. Condemning a man who loves you to public, humiliating death? That's a level of soul-crushing personal evil worthy of Planescape: Torment. The Practical Incarnation would be proud.
Dragon Age II continues the tradition; the game's Grey and Gray Morality means that there are compelling arguments for and against a lot of the things you can do, but there is no justification for some of them. For example: one of your companions, Fenris, is an escaped slave on the run from his blood mage master. When his master inevitably catches up with him, you can help Fenris fight him off... or you can hand him over, saying you don't need him any more, leaving Fenris so gutted by your betrayal that he leaves with the slaver without a fight.
It's even worse if you're romancing Fenris and Danarius makes note of his former slave's "skills"; the betrayal is so much worse when you know what Danarius is going to do to him.
If you're the sort who enjoys stomping people's hearts into bloody pulp, romance Anders. Listen sorrowfully as Anders pours his heart out to you, all his fears and terrors about losing control and hurting you. Sleep with him. Enjoy his declaration of love, and how the templars will never tear you apart. Then dump him, citing his performance, or lack thereof, as the reason. Alternatively, keep him, and then execute him at the end of the game. It's up to you.
In Baldur's Gate II: Shadows of Amn, the player character can set companions characters up for some really brutal party conversations. Viconia's romance also allows the player to take her to bed when it's clear she'd rather not. Thankfully, this ends the romance.
In the Destroy All Humans! series you can do many horrible things to the citizens such as dropping them from high heights, mind tossing them off into the distance, burn them, drown them, blow them up,etc.
In the prologue of Golden Sun, you encounter a guy who's apparently wounded and asks if you think he's going to die. Answer "no", and he realizes he's not actually hurt. Answer "yes", and he dies.
Dark Dawn brings Slap Psynergy to the table. Its main canon uses are bopping statues on the nose, slapping sleeping things to wake them up, and knocking Djinn and friendly pirates down from high places. Said pirate is understandably peeved with us for doing so.
However, the dev team thought of one more: You can ring the emergency gong in Tonfon, sending the city into a panic, and then blame a guard for the false alarm.
Dark Dawn also has two locations where you can see seemingly-inaccessible Mercury Djinn. The trick as it turns out is hitting them with Fireballs so they dive in the water to cool off, and then you either drain the water or find a local fisherman to get the Djinni for you (by catching it on a fishhook).
In Golden, however, there is Valentine's Day. All of your girlfriends will invite you out. You can only spend time with one (or reject them all). However, your four party member girlfriends still give you chocolate, but it's very obvious that they can tell something's up. You Bastard.
The above is true in Persona 3 as well, but if anything it's even worse: not only can you date all five eligible females at approximately the same time, you *have to* if you want to max out all the social links. (Persona 4 allows you to advance social links with female characters via platonic friendship, 3 doesn't.) There's one scene that calls the player on it, but there are no actual negative consequences so long as one is careful about timing meetups with the various girls.
A non-romantic example is the social link of a small child whose family is breaking apart. After one of her parents hits her, the player is provided with the option to tell her that everything was all her fault (possibly the most sadistic example in Persona 3).
Persona 3 also includes an aversion, in that if you act like a total dick to your Social Link members, you can get punished by "reversing" a Social Link, preventing it from advancing (though this isn't permanent.) If you're too cruel to them, you can also break the link permanently.
Persona 2's initial protagonist, Tatsuya Suou, is canonically kind of an asshole. Play the game right, and he becomes a nicer person for his experiences. That said, you can also play it wrong. Want to slap your kindest party member while she's having a trauma-induced panic attack? You can do that. Want to cheat on two of the dateable party members with the third? Yeah, you can do that too. Want to kill the headmaster of your school? Totally allowable. Most of the cruel options will instantly lock you out of some of the best Personae in the game, but those last two have no in-game consequences at all. Killing the headmaster does tweak the plot slightly, but not seriously, and it can be argued that he was dead anyway and the other option would have resurrected him. That said, you still confirm his death.
Kingdoms of Amalur: Reckoning allows you to toggle friendly fire so you can freely slaughter helpless villagers. One of the loading screen tips even encourages you to do it! And of course there are the obligatory dialogue options that let you blackmail/extort people.
In TaskMaker and The Tomb of the TaskMaker, you can kill any NPC with a Neutral alignment. This includes shopkeepers, guards, etc. And if you're feeling really cruel, use a Restart Place spell to reset the location and do it again… and again… and again… The former game takes off a small amount of points, while the latter doesn't have a points system.
You can also do this with Good-alignment NPCs, but killing them will take off a lot of points and knock down your Spirit (or just knock down your Stamina in the sequel). Also, there are two Good-alignment characters in each game who will render you permanently drunk, deaf, and blind if you kill them.
A mild example occurs in Legaia II: Duel Saga. In the town of Yuno, there is a small child building a massive snowman. Lang has the option, when the kid isn't around, to go up to the snowman and knock it down; the kid is visibly upset at his hard work being trashed, but sets off to rebuild it. Do this enough times, and the kid calls Lang out on this, and Lang receives the title of "Bully".
Evil Islands: At one point in Suslanger you're required to sneak into city choke full of guards and ordinary city folk. Normally killing non-aggressive NPC's such as deer, rabbits or workers yields very low rewards. Here, however, townsfolk drop amounts of gold that can make you reconsider going on a city-wide killer spree... that is, if you don't get caught.
In Robopon, you can sell your Robopon just to make some cash.
In the Card Battle game Yu-Gi-Oh! Zexal Duel Carnival, you can challenge a lot of folks from the anime who don't normally duel, like Yuma's kindly grandmother, Nelson's mom, and all manner of young children. Most of them are incredibly easy and have cards that most duelists wouldn't be caught dead with, and you may feel like a big rat after pounding them with direct attacks. Even worse, Haruto. Yuma's storyline requires you to duel him (although he's actually got an okay deck) but if you're a fan of the anime, you won't like yourself is you manage to win by a Curb-Stomp Battle. (And he still likes you for "playing with him" after you do!)
The Genocide Route as a whole counts, but Papyrus's fight is a particularly stark example. There is absolutely no reason to kill him. In fact, the only way to do so is to deliberately ignore his offer of mercy, and attack him after he's already spared you. Made even worse by the fact that no matter what you've done so far, he will never try to hurt you himself.
There's one cruel act you can only do when not on the Genocide Route. Fleeing from Undyne into Hotland causes her to collapse from heat exhaustion. There's a nearby water cooler you can use to cool her down...or you can dump all the water out onto the ground in front of her.
Resetting the game after the Pacifist Route. The monsters are freed and the barrier is broken. The monster race look forward to an uncertain but hopeful future as friends of the humans above ground, and everyone is happy. But there's only one small problem: You. You hold the power to reset the world, and take away the happiness you brought everyone. And you can then play a Genocide Route, and no-one (except possibly Sans) will know that the nameless child wandering through the Underground slaughtering them all was, once upon a time, their best friend.