A punk is a man who is a quitter and a coward. Punks put up a barrier between themselves and others that keeps them from being challenged, because to challenge a punk is to defeat him. He won't put up a fight. He depends on society to guard him even though it may involve his anti-social behavior. Punks are often sycophants. This is their best barrier. They need the protection of someone powerful, so they may become bootlicks, toadies, brownnosers and suck ups. Punks play word games to avoid accountability. They do well in the company of authoritarians.
The little bitch is a man who feels that he is owed something and therefore spends a lot of time advertising his discomfort. He may or may not be a punk as well. A little bitch may refer to himself in the third person as though the very fact of his existence should compel people to care. Easily offended, little bitches are meticulous in their deportment and can't imagine why the rest of the barbarian world doesn't. Thus, a little bitch is always trying to explain things. They must get their two cents in about how the world should be, and what a damnable inconvenience that it is not. A little bitch will readily confess to being a little bitch but they have much more glorified labels for themselves. True patriot, keeper of the faith, defender of the weak and other such grandiose delusions.
A dickhead is a man who is singleminded in intent and unsubtle in pursuit. It might because he is unsophisticated and incapable of subtlety. It might because he stupid and unable to see his welfare in any other goal but the one he doggedly chases. It might be that he is cunning and ready to exploit because he simply has no empathy, much less sympathy. A dickhead is certainly disagreeable, but it might be in the interests of others to see that he succeeds in his monomania. Such a dickhead is also known as a tool. The difference between a dickhead and a bootlick punk is that the dickhead is indeed ready to fight. He has all the conviction of his single principle. He is possessed of that kind of integrity.
An asshole is a man who is capable of being subtle and agreeable but has decided not to be. This may be for a particular subject in which case we call him a partisan. It may be for a particular type or group of people in which case we call him a bigot. For those circumstances in which the asshole is forced to deal with the object of their derision they will display characteristics of a punk, a dickhead or a little bitch. Assholes are not necessarily vicious or stupid. It is possible for an asshole to be well-informed and empathetic. In fact a majority of such assholes will warn us ahead of time that they are. I myself have striven to be such with the expectation that people would say, "Yes he's an asshole, but he's my kind of asshole." Such assholes we tend to call advocates, champions and geniuses.
A bastard is a man who, for some generally traumatic reason, is unwilling to be gracious or forgiving under any circumstance. A bastard is likely to be a very specific kind of asshole, the sort that adheres without mercy to some obscure set of rules. One can only hope that a bastard is consistent, but it doesn't matter if they are. They are miserly and uptight and refuse to be good sports about anything, except perhaps when they are cutting deals for immunity. Bastards who fail to become powerful or resourceful will degenerate into little bitches. Yet as the classic definition implies, the bastard may have been truly wronged or abandoned, leaving them wounded and incapable of letting bygones be bygones or sleeping dogs lie. Needless to say bastards are often capable of translating their pain and misanthropy to bring themselves esteem. We call such bastards diehards, hardliners, prophets or witnesses for the prosecution.
A douchebag is a combination dickhead and punk. He neither cares what people think of his ambition nor is he often capable enough to pull it off. On the rare occasion one becomes aware of a successful douchebag, isn't it because they merely become famous in failure? What the unique quality the douchebag has is his categorical ability to offend, an effect of which he is generally oblivious. When confronted, the douchebag will demonstrate his inclination towards dickhead behavior or merely punk out. Douchebags tend to cluster and attempt to draw territorial lines within which they feel safe.
These six varieties are sufficient to cover the nearly exhaustive majority of the population of disagreeable men, but I don't mean to suggest that women cannot be or are not capable of similarly vicious deportment. I'm simply not interested in being inclusive in that dimension. Character and psychology being universal as they are should suffice such that you can interpolate the rough equivalents in feminine terms should you feel the need. I will not assist. Where I come from, this is called being a gentleman. I wouldn't be an asshole about it if I were not besieged by little bitches.