Manipulation is a form of social influence. Everyone does it to varying degrees and it, like any tool, can be used for good (such as persuading an unhealthily obese person to lose weight) or for ill (such as conning people out of their life savings). There are many different types, degrees, reasons, and ways to manipulate people.
I bring this up because I often see, in Ranma ½ fanfiction, Ranma not being very manipulative when the manga incarnation of Ranma is extremely manipulative. He is far more manipulative than any other character in the series (the anime version is less manipulative). As far as I can tell there is not even one volume in which Ranma does not at least try to manipulate someone in someway. In fanfiction, Nabiki tends to be portrayed as the most manipulative character; probably because she is (manga version) avaricious, opportunistic, unscrupulous, fairly hedonistic, and borderline sociopathic (she shows absolutely no remorse for her actions). A lot of the traits usually ascribed to Nabiki in fan fiction (such as spying on people to find out their secrets, being manipulative, setting up elaborate plans, knowing what is going on, etc.) apply a lot more to Ranma than Nabiki.
I do not view all of Ranma's machinations in a positive light. That said I do usually, though not always, see them as being justifiable. In fan fics I often see Ranma resort to violence too quickly and too frequently. That is not his standard modus operandi. Ranma will usually try to be diplomatic (talk things through) and when that fails (usually because the other person really has no inclination to talk things through) he tends to resort to things like manipulation and deception before proceeding to violence. Violence, in most situations, is his last, not first, resort.
In a related note; Ranma's interpersonal skills are often viewed as being a lot worse than they are shown to be in the manga. While there are some situations in which his social skills are inadequate (mostly in situations involving romance or the possibility of romance) they are for the most part very good. He can explain things (most people do not listen or hear only what they want to hear which is not his fault -example Ranma tried to explain to Akane about the pressure points on Miss Hinako with the use of a visual aid we are shown that Akane selectively edited the conversation), he tries to be diplomatic (for example with Ryoga, Ukyo, Akane, etc.) that the other people have no inclination to talk it out is not his fault (this is something he has actively complained about for example in one volume, volume 11 by Japanese/online scan count, he tells Akane "when have you ever let me explain things before hitting me" after she said why didn't you explain it). He has no trouble socializing with people at school (hangs out with two kids). One of his faults though is he doesn't know how to socialize with girls as well as guys (probably because he spent most of his life around guys not girls, he was shown to have gone to an all boys school). For the most part he talks to girls as if they were guys for example guys would slap each other on the shoulder which is what Ranma did to Akane at least once. A couple other things which may contribute to people viewing him as having poor social skills is that he is out of touch with popular culture which is a hindrance amongst teens (he is a martial arts nerd) and he sometimes speaks without thinking about the ramifications of his words (he gets in more trouble from telling his honest opinion than he does when he lies). The fact that he is capable of manipulating people implies he has better social skills than many people assume.
Before I get further side tracked, here is a list of some, not anywhere near all, of Ranma's machinations:
1. Being a matchmaker.
- tried to set up Cologne and Happosai, did setup Ryoga and Akari, was going to teach mirror clone how to properly pick up guys, etc.
2. Fake or create an injury to garner sympathy
- multiple times, for example the time he purposely hit himself with nunchucks to garner Akanes sympathy
3. Donning a disguise and pretending to be someone else
- all the time, pretended to be Ryoga's sister, maid, fiancee, etc.
- Few actual attempts for example tried to blackmail Nabiki with what he thought was a love letter. Has searched multiple peoples rooms looking for things to use against them (for example he searched Nabiki's room multiple times). Very much implied that he would blackmail people were he to find things to blackmail them with and had a reason to do so.
5. Emotional blackmail
- Fairly frequently for example with Picolet Chardin III told him, paraphrasing, if you love me you'd tell me the secret of the technique.
- Few times for example threatened the Cherry Tree spirit with an axe.
7. Enjo kōsai
- Going on dates to get stuff such as his date with Tatewaki or Shampoo.
- Rarely uses this since the majority of characters do not want anything he is willing to give. Example: To get Tatewaki's love (to win the competition) she gave him many objects such as a handmade scarf, love letter, bottled water, etc. or Happosai to get him to lower his guard.
- Teases people commonly. Was attempting to seduce Akane to get rid of the Dogi.
- Tried to slip Tatewaki and Densuke drugs in their food, used chloroform on Happosai, got Happosai drunk, etc.
11. Elaborate plans, some involving many people and multiple steps
- In an attempt to get Happosai to change Taro's name he came up with an elaborate plan that involved writing a play, using suggestion incense, drugging Happosai, getting multiple people to work together, etc.
12. Guilt trip
- Made people feel guilty to get them to do stuff. For example, Akane when he pretended that he destroyed the instant man spring water.
- To mess with Ryoga, Akane, and once he went a step further than just the voice and used an unconscious Tatewaki like a literal puppet to force him to apologize to Kodachi.
14. Pretending to be beaten or apologizing then attack when guard has been lowered
- Pretended that Ryoga beat up an innocent normal high school girl to get him to lower his guard, pretended to bow and beg to Shampoo before attacking her, etc.
15. Scare tactics
- Used rubber snakes and other supposedly scary items on the school girls.
Okay I feel I have listed enough to make my point, Ranma is extremely manipulative. That is no where near a complete list and the labels/order for them is somewhat arbitrary. The thing is they are not one time things or isolated incidents this is common behavior for him. He is always manipulating people and playing head games. It is even a major part of his fighting style; he uses distraction (like look over there), underhanded tactics, fake incapacity, duplicity, trash talk, insults, etc. all the time. He exploits character flaws and weaknesses (to list them all would take a really long time) but basically if a person has a weakness (such as an addiction to women undergarments, anger at seeing breasts, an exploitable curse, etc.) he will use it against them (provided he has a reason to). He is shown to actively seek these types of things out (like searching Nabikis room). Because of how manipulative he is (and how much the characters around him are jerks) he is constantly suspicious of other peoples behavior and motives for example Happosai's friend Lucky and Nabiki (the open and trusting Ranma seen in some fan fiction is nothing like how he is in the manga).
Since this is a post on how manipulative Ranma is I will now say that not only is Ranma manipulative he is actually pretty good at messing with people. Ranma's machinations usually work on their intended target (he reaches his intended objective, though he is somewhat shortsighted on occasion and neglects to plan for what happens after he reached his objective). When they do fail or backfire (usually after he reached his intended objective) it is generally for one of these reasons:
1. His morals (or sense of honor) kick in. This results in him realizing how much of a jerk he is being, starts feeling sorry for his victim(s), and begins to feel guilty for his actions.
- This is actually why people like Nabiki are able to get one over him and what prevents him from being a monster. If this didn't happen things like Happosais death would have happened (when Happosai was weakened by Ranma, Ranma felt sorry for him and did not finish Happosai off or let the fathers do so). Basically he is too sensitive to other peoples feeling, if a girl, Ryoga, or even Happosai start crying or something he will feel sorry for them and try to help them (no matter how much trouble they had caused Ranma earlier).
2. Third party interference.
Things like Akane revealing that it is really him in disguise or Soun and Genma interrupting.
3. Opponents or allies taking unexpected and unforeseeable actions.
- This is a major problem for any plan. You can make plans based on the most logical thing a person would do or based on past actions but people do not always do the most logical things and can screw up your plan no matter how well made it is. For example Happosai deciding to kill baby Taro instead of taking the much easier and more logical route and giving him another name or his allies (Mousse, Ryoga, etc.) deciding to back-stab him.
This was actually one of the very first posts I had intended to write but I kept putting it off. While I do feel that this post serves its intended purpose of pointing out that Ranma is very manipulative it still doesn't really feel complete to me. I sort of feel like listing the justifications and context for Ranma's actions (as I had stated the majority of his manipulations are, imo, justifiable based on need or the actions of others and context is important because Ranma comes off as being a much worse person when the context for his actions are left out). I was thinking about explaining how being primarily opportunistic (Nabiki) is different from being manipulative (Ranma), though there is overlap (major difference being that one waits for a situation to come about and takes advantage of it, the other will do that but also will create a situation to take advantage of if one doesn't already exist).
Some thing else I felt like putting in the post but wasn't sure where to put it (that is why it is here at the bottom) is the fact that Ranma, and the majority of the cast, are teenagers. From a biological stand point. The prefrontal cortex doesn't finish developing until around the age of 25. Teenagers rely mostly on the amygdala which is the primary seat of emotion in the brain which leads teenagers to over-focus on the emotions of the immediate situation. The prefrontal cortex which is still developing in teenagers deals with initiation, planning, sustaining attention, organizing action, inhibiting reactions, shifting from one task to another, and regulating emotion. What that basically means is that I would expect fanfiction that has an older Ranma in them to have him be even better at manipulating and tricking people. At the time of the manga Ranma is impatient and somewhat shortsighted. That is something I would expect him to grow out of. While his plans generally work up to the point he thought them up he often failed to plan for what happens after he reached his immediate objective (or that it might be better to wait a little while before implementing his plan or think them through longer). While he is extremely good at improvising (for example in the battle with Herb he improvised a change of the Hiryu Shoten Ha based on it principals and correctly anticipated Herbs actions) it would still have been advantageous for him to have contingency plans already set in place.