The cliche nice guys finish last can set everyone back. It paints of picture of jerks finishing first and makes some think that is the only way. I used to be lost in the distinction, but a jerk is never what you want to be. The reason they do better than nice guys is they have some attractive qualities that nice guys don't have (yet they still have a lot of terrible ones). Why would you want to intentionally hurt people and just be considered an awful person to reach some end goal? You can take the good qualities of both a nice guy and jerk and be who you would really want to be, someone others can look up to as well. So what is the difference?

Nice Guys: They have no center of self. They try to please everyone in hopes of gaining something, even if it hurts themselves. They bend to other peoples opinions and take things personally. They are chameleons, everchanging in hopes of being liked. They think this will be enough to win over a woman. This is who I used to be and who I am still fighting. I used to imagine being the white knight that rides in to save the day.

Jerks: They do whatever they want no matter who it hurts. They please themselves and are egotistical. They don't listen to others, don't help others, and generally are out for their own gain. The attraction to this comes because he seems like a leader: someone who commands, who is strong in their opinions, who knows what they want. However, he hurts people, he shows no care, and he is someone you cannot trust.

Well Developed Men: They have a strong center of self. They have strong beliefs and opinions, but are willing to listen to others' ideas and potentially change their own if they see fit. They don't take criticism personally, but will ponder over it and take anything beneficial from it. They will help others they care for or out of the goodness of their heart, but generally not if it hurts themselves or if it is to get something in return. They don't try to hurt others, but don't try to please either. They are direct in what they want, but not in an overbearing, inconsiderate way.

So what does this look like in different scenarios?

Someone is mean to them or crosses a boundary:

Nice Guy: Apologizes and tries to ease things over. Isn't looking for a fight or an argument and will generally agree with the aggressor.

Jerk: Tries to fight the person. Calls him names and tells him he is a dick who is fat and ugly.

Well Developed Men: Tells the aggressor to knock it off. If he does not respect the boundary, he decides to end communication unless something more is absolutely required.

Someone asks them for help:

Nice Guy: Agrees without a second thought, especially if it is an attractive girl. She wants you to help her with homework? Definitely! She asks you to drive her somewhere? Sure. So what you have a test you need to study for the next day.

Jerk: Says no unless there is something in it for him. Maybe asks her for money or a sexual favor: a tit for tat.

Well Developed Men: Asks himself if he cares about the person. Would he do the same for a fat, old man? If so, sure. Does the person care for him and genuinely would do the same for him? (not a tit for tat, but a mutual relationship of care and trust). Then, he does it. Does he have the time to do it without interfering with previous plans or something else that is a necessity?

A girl talks about her boy problems:

Nice Guy: Listens no matter how long it takes. Maybe asks her to go more in depth or offers a shoulder to cry on. Generally listens to all her problems and tries to help to be better than the guy she is complaining about. (Note: This is totally alright with girls who are well established friends in my opinion and you actually have no ulterior motive.)

Jerk: Tells her to be quiet, and that he doesn't care. Tells her he should've just fucked himself instead.

Well Developed Men: Talks to her if she is a genuine friend that he cares about in a platonic way. If not, he politely acknowledges what she says and shifts the subject to something they are both interested in.

An argument or disagreement comes up:

Nice Guy: Agrees with the other fairly quickly. Isn't strong in his own beliefs and feels wrong or stupid for believing what he does.

Jerk: Doesn't even listen to what the other has to say. Just talks louder and more quickly than the other.

Well Developed Men: Has a true discussion with the other person. They share points and listen, telling each other where the disagreements are and being open to changing opinions.

Wants to Hit on and talk to a girl:

Nice Guy: Goes up and says hello. He talks to her about whatever she wants and will feign interest. He doesn't even tell her his interest in her, that he finds her attractive, or that he wants to take her on a date. He pretty much just hopes something will happen. He makes no moves and does nothing too risky or aggressive.

Jerk: Goes directly up to a girl and tells her he wants to fuck her. Maybe he grabs her on the ass with no signals to do so. He is loud, obnoxious, and aggressive.

Well Developed Men: Talks to girls and is open about his sexuality and what he wants. He doesn't put up with shit tests, a girl being rude to him, or listening to her problems. He directs things while taking into account what she may want to do or talk about. He still has his center of self and doesn't try to please her or change his opinions or hide anything. He tells her he wants to take her on a date or that he finds her attractive or that he disagrees with her. Maybe he tells her to stop being rude if she is. He doesn't put up with what he doesn't like just to get lucky.

TLDR:

Nice Guys: Asks what does everyone else want and believe, and doesn't give a shit about himself.

Jerks: Asks himself what do I want and believe, and doesn't give a shit about anyone else.

Well Developed Men: Asks himself what do I want and believe, while making sure not to hurt others or only care for himself.