I wanted to repost here to analyze any character in DMC4, from every Devil down to the last Human.
Nero. He's a fierce teenager. Probably more mature than Dante or Vergil were in Devil May Cry 3. Cocky and a smart-mouth but not as much as Dante of course. (You can see that even some of the bosses said to him that his insults had no effect on them). He also does not seem to care about pretty much anything but Kyrie. He shares some Vergil characteristics when he angers because of what may have been done to her. (For example when he failed to save her from Agnus Angelo, he reminded me of Vergil when he "failed" to open the gate because he did not know that Lady's blood was part of the "key"). However in the game his character remains the same. No character development, and it's not his fault as no one had enough of it in that game. But the game was kinda "for" him, and that's a little disappointing. His only change is that he doesn't hide the DB from Kyrie anmorere. Having attributes of both of the twins made him different and same with them in the same time, which isn't a bad thing. His cool moves and style, made the fans love him just for it (maybe his appearance too for female fans) and to be honest I also am content with that. He is quite successful as a character, but personally I wouldn't like for him to take the "lead" in a game named Devil May Cry. Some "side DMC game" with Nero would be alright though.
Dante: He doesn't really have a role in the game. For me I'd say that all this was just another work for him and he just happened to have fun with it. However he rules, since they fused his DMC3 and DMC1 character into one, make him closer to the ideal Dante of every fan.
Kyrie: She doesn't really do anything. She just is the damsel in distress. However she isn't as annoying as other "damsels in distress" are which is a good thing. But she really is in the game only for Nero to have an objective and the motivation to accomplish it.
Credo: Serious, fair and some other good points, but his role is shadowed by the others. I really would have liked for more info about the guy and his relationship with Nero (as they were almost like part of the same family) but yet again they killed him before he could do anything. However I was annoyed that his heroic deed was useless. If they could at least make him a little more useful and not kill him maybe he could offer more as a character...
Gloria: Eye candy for male fans as Steven once called her in a conversation we had. And a plot-hole to the series. I never did understand why Trish needed to do that. And she even gave them Sparda. For what? To make things more interesting for Dante? Give me a break.
Agnus: That guy may be more well-made that most of the others in fact. First of all he's one of the villains from the start. He's the evil genius type that although he is faithful to his master's desires his best interest is his research. He actually had the power to "tame" devils and put them into armors, swords and other stuff. Nice addition if you ask me. And the fact that those demons aren't as strong could be explained since the demons possessing other things aren't as powerful as their real form. (Unless we are talking about parasites like Echidna's children). Also, like some of the well-known geniuses he has some flaws, his t-t-t-t talk. That was nice, and funny when Nero taunted him for that. And also being lost in his research, another scientific feat. You can't call him original, but it suits him in the end. Even his moves in bosh fights reflect his nature. (Summoning, draining health). I am not a fan of him, but I don't hate him either.
Berial: Ok this guy is the most disappointing of them all. He has the coolest boss design in the game (Dante excluded), he knows Sparda, recognized Dante, being able to boast for being the conqueror of the fire hell (since he brags about it, it shouldn't be an easy feat to accomplish). Yet he dies, without doing anything..only giving us the almighty Lucifer. Ok, I envisioned the guy as Phandom from DMC1 (cunning, vengeful, escaping and returning) and Beowulf from DMC3 (super powerful, deep hatred making able to search for Sparda's scent while blind), but he just chickened out with Nero and tried a suicide attack on Dante. Lame Mr Conqueror.
Bael & Dagon: These little insignificant guys, were better thought than Berial. First of all they are not as dumb as they look. Predators. The opposite of Berial, crappy design, better though caracters. Hiding in the blizzard was a new experience in DMC world. And being able to drag him out as well. Plus them having, other family members is so right. I mean is a gate to hell. It's MORE than just logical that more devils would want to come out isn't it? As for them being stupid and stuff, well you can't have it all. At least they served a bigger purpose than Berial in my eyes.
Echidna: She's also better thought than Berial. Since she is so powerful (she is a boss alright) and a devil (evil, etc.) it's also logical that she would try to conquer a place for herself and change it according to her own taste. Spawning more devils was nice and a normal action too. She also gave a nice Devil Arm although I don't really use it, I'm sure others love it.
Trish: If Dante was facing the Doomsday in the face of the savior, then Trish, also known as Boobsday was heping people run away. Okay I agree that is normal. But..if you see more clearly little Trish, all the order's machines/devils/whatever kill the demons before anyone getting hurt. I guess she helped those near the Savior since Dante and Nero wrecked the place around him, but then again...
Also as I said again what was the purpose of "bringing Sparda in the spotlight" as Lady asked?
Lady: Eye candy Number two. Nothing to say about her..really. Neither good or bad.
Sanctus: Ok, seriously, you old guy there could rival Arius in stupidity. If someone told you're related I'd believe him. Crap plan even for a religious guy. A religious guy believes in some god, doesn't create him. And I don't see how the Sparda and Yamato helped the Savior either. He could be the cunning old fox behind everything, but he was nothing. Really disappointing..