A lot of characters here tend to be in the context of something along the lines of overpowered or unoriginal. Though they are not Naruto characters, which is a good thing, it does not really help if your character lacks any genuine trait that would make him or her believable or within realistic limitations. So here, I will be describing how I go about creating characters, in general. This guide should not be used, by any means, as a one-size-fits-all: different people go by different methods.
Make sure you note that creating characters with really close attachments to characters already created in the universe you are using, assuming those characters are not your own, are frowned upon. The same goes with creating a character that is essentially a copy of a previously existing character (referred to, by some, as carbon copying).
Step 1: The purpose of living
The first thing you should think about is why your character exists. Everyone have goals that they strive for, whether they are living, now-deceased, or fictitious beings. Why is your character stepping into that spotlight: is he searching for love? Power? It could be as simple as wanting a glass of water, for all I care, but all characters have a purpose for being out there in the world. Without a purpose, your character's awesomeness and role-playability will be dropping like a rock in mid-air.
Step 2: The goal
Now you decided on what your character wants to achieve in life (or whatever life your character is in), how is your character going to go about achieving that goal? Would he turn to piracy to get the money to pay for his sister's operation, or would he wander about as a vigilante in order to help the poor?
Think about the realistic aspects of arriving at that goal. If you plan on assassinating the king, there should be steps to be taken in order to be able to approach the said king in the first place, for example.
Step 3: History
With a goal, you need to explain why he or she has that goal to achieve. Did the ghastly murders of your character's parents cause him or her to wage war against crime? Most of this is self-explanatory, but remember to keep everything in realistic proportions (if it seems unrealistic in the universe you are creating a character for, make sure you have dead good reasoning as to why that phenomenon happened).
Step 4: Personality
It's a widely accepted fact that a person's personality is defined by his or her past. If your parents were killed by criminals, the likelihood of you being nice to a crook is pretty slim. This might seem to be the most troublesome portion of the creation process, but it is the most essential part to bring your character to life.
Step 5: Gears, tools, skills and appearance
At this point, all of basics of your character have been explained and fleshed out. Now, comes the part of bringing together a visual representation of your character. Common sense plays a major role in this: a spy will have tools that would help him or her spy on people, a Jedi Master will have a lightsaber, etc. However, be weary as to not overload your character with equipment. It's not easy to carry around ten, full-length katana without help of some sort.
No one learns skills for no reason whatsoever. You are probably not going to learn how to design houses if you are going to be a meteorologist. Keep that in mind.
Your character's appearance should also make sense: if your character lives in Medieval-era Europe, he or she is not likely to be wearing khaki pants and t-shirts. If your character is the CEO of a major corporation, he or she is probably not going to dress in a sports jersey and blue jeans on a typical day.
Realism matters, no matter what universe your character lives in. If you are standing on land, the likelihood of you not falling up into the sky is 99.5%. If you are shot in the head at point-blank range in an ambush, the likelihood of being able to dodge that bullet is slim to none.