Someone else can waste time with this case.
This is what I say to myself every time I begin to reply to you. But my willpower is weak, and I end up replying anyway. I don't know why, because this is the exact response I get from you every time. You never admit fault, you always just make a giant public display of "omg I literally can't even, you're soooo stupid I can't talk to you" and stomp off trailing reaction gifs and emote text in your wake, not one salient point or solid line of logic between your first post and your last.
How many times have you made a post exactly like the one you made just now? I've posted on these boards a lot, but I've lurked even more. Whenever you argue, either that type of post ends up happening, or the thread ends up locked, and I'm not even involved for most of those. You can keep blaming literally every person who ever disagrees with you, or you can ask yourself how much of the problem lies with you.
Anyway, derail over, back to the original point.
@Foxtrot94 I like your interpretation as well, but as
@Innsmouth Mentioned, Nero is supposed to have Sparda's blood and I don't think making a pact with Vergil's soul would give him that. And I kinda like the idea of Vergil having a son so I'm a little biased
This is where I'm at too. Prior to the events of DMC3, vergil supposedly drops off the face of the earth for a whole year (and even before that, it's never specified exactly what he was doing). When he shows up again, there's just enough clues to conclude that how he behaves is more extreme than he normally is.
The theory is that vergil has a son somewhere within that one year gap, and the timeline would fit around that. Lady goes from being something like 15 to in her late 20s or 30s for DMC4, and nero is portrayed as a cocky teenager at around 16 or so. Dante is aware of vergil's actions prior to that one year of absence, and then vergil goes off and dies immediately after resurfacing. Since dante is unaware of nero's bloodline for most of DMC4 (sanctus even taunts his ignorance of this at one point) that one year gap has to be where nero is conceived.
Now here's where things get a little more speculative, so take everything past this line with a big grain of salt, unless I specifically mention it's canon
The theory is that vergil hooks up with a nice human, and actually starts to settle down into the role of happy dad, following in sparda's footsteps and seeing something worthwhile in a human. During this time with his guard down, he's attacked, the woman dies, and nero is lost, presumed by vergil to be dead (and later discovered by someone else who takes him to the doorstep of the order, as it states in nero's DMC4 bio). Vergil's inability to protect himself, his son, or this mystery lady push him over the edge, and the pain of losing a loved one is too much, to the point where he feels the only option is to rid himself of his weaker, feeling human half. This is why he goes on his rampage killing humans and seeking entry to the demon world; because he's done with being human, and wants to be as uncaring/unfeeling as a demon.
Additionally, you could also suggest that vergil's line at the top of the tower: "without strength you can't protect anything" isn't referring to dante's inability to protect himself, but a reflection of his own failure to protect nero and his mother.
Once again, highly speculative, but it would add some much needed depth to his character, so I like to believe it.
Oh, and also the origins of nero's arm. In his official bio, it states that nero is wounded in the shoulder by a mysterious demonic weapon (in the same fight where red queen is damaged and sent for repair) and at first he believes the wound to be infected or poisoned, but soon realizes his arm has transformed into a source of demonic power, and trains with it in secret. That much is canon.
More speculation here. So when powerful demons in the DMC universe die, their essence forms into a weapon bearing their name and some of their traits. Vergil is a powerful demon in the DMC universe. In the description of nero's injury, the demon is not wielding the devil bringer, but the derpy equivalent of a demonic pointed stick. Not that impressive, and obviously improvised, but still powerful enough to damage the red queen and wound nero. The speculation here is that Vergil, the weapon, retains some shreds of consciousness (or maybe pride is a better word?) and upon being found by a lesser demon, he refuses to awaken as a true weapon for something so unworthy of him. The weapon is still pretty good, even as an inert object to just swing around, but nowhere near its full potential. When "vergil" pierces nero, he comes in contact with his blood, and the weapon recognizes him as someone worthy, transferring himself inside of nero's arm and transforming it. Yamato has always been vergil's weapon, and when nero encounters it, yamato recognizes vergil's ownership and seeks out nero's arm, to reunite with its old master.
Nero has even described his arm as whispering to him, saying some very vergil-sounding stuff, and he can only access devil trigger while holding yamato. While in this state, an oversoul that looks a whole lot like vergil's demon form protects him (the arm mounted sheath is the most obvious feature) although the projection itself looks kind of dazed and not all there in the head.
There's other stuff, but that all stretches the bounds of reasonable speculation, even for me. Also this post has turned into a huge wall of text, so that can be for another time.