Lady may be a Badass Normal, but she's still just a human with guns and no armor, yet she cuts through hordes of baddies. One can only wonder therefore, how those same demons would fare against a whole army of soldiers with tanks, attack choppers, etc. Even more serious demons like Leviathan would be reduced to sushi by a good aerial bombardment. So if muggles clearly do it better,where the hell are they when you need them?
2 shows that there are parasites that can control choppers and tanks, so possibly might not be the best choice. And keep in mind that Lady can cut through hordes of demons because not only is she experienced, her arsenal is loaded (Kalina Ann being the primary weapon) and most likely modified from the standard firearms.
5 release trailer further shows that the military is woefully unprepared for a demon invasion.
In the form of a What the Hell, Hero? for Sparda, several fans have wondered why exactly Sparda didn't leave his family with the Vie de Marli for safekeeping considering that he helped them kill an evil demon god (thus meaning that they probably owed him a favor) and that they were more than capable of warding off some measly demons sent by Mundus. The potential problem is never addressed in-game.
Considering Sparda's age, it's quite possible he helped the Vie de Marli decades before meeting Eva. We also don't know what happened to Sparda, maybe he planned to do it but was killed before he could.
The Vie de Marli could fend off common mooks, but what if more powerful demons were sent, or worse Mundus himself paid them a visit, like in the reboot?
The names of Sparda's keepsakes to Dante and Vergil, Rebellion and Yamato. Sparda rebelled against Mundus and sided with the humans, and Dante carries this with him as he rejects his demonic heritage. Vergil, on the other hand, is precise and quick with his sword swipes, even killing stronger demons with little effort.
Dante picking up his Heads or Tails? quirk in 2 may seem strange, using his coin several times throughout the game, before it's revealed that it's a trick coin where both sides are heads. However, in a bit of a Call-Forward, Dante in the first episode of TAS promptly picked heads when Morrison challenged him to a coin toss on whether or not to take the job of being Patty's bodyguard. He lost the bet with Morrison (it was tails), and it's been stated that he's never been that lucky when it comes to gambling, hence the quirk seen in 2.
The legends of Sparda state that he fought against legions of demons by himself. A difficulty mode in 4 allows you to fight of legions of demons by yourself. The name of said mode? Legendary Dark Knight. (Bonus points if Dante is using the Sparda costume)
Vergil's moveset in 4 is much flashier than before. However, considering that his story in 4 takes place before 3, it makes sense that he was not as precise then, even needing the Summoned Swords to help him perform Trick. Vergil hasn't perfected his Darkslayer style at that point in his life. The Concentration Mechanic is basically proof of this.
Also, notice how some of his moves (namely Yamato Combo C) have him wildly flailing Yamato. Hell, he straight up borrows some of Dante's moves (Kick 13, Million Stab, etc.).
In 4, Nero could (theoretically) use Devil Bringer to save Kyrie on at least two occasions. However, the only things you use the Devil Bringer for in-game is as a grappling hook against non-corporeal targets or to lay the smackdown on the bad guys, neither of which requires a delicate touch. Perhaps the Devil Bringer is incapable of being used in a gentle manner?
Also, rewatch the cutscene in which Kyrie first sees the Devil Bringer. Nero tries to hide it behind his back, which would be hilarious if it weren't so tragic. He doesn't even want her looking at the mark of his curse (as he sees it), let alone coming into contact with it. It was no accident that the final cutscene of the game had Kyrie interlacing her fingers with those of the Devil Bringer - it was the ultimate sign that she had accepted Nero for who he was.
In the second Nero vs. Dante battle, Nero's final attack is identical to the one Vergil used in 3 to defeat Dante. However, Dante stops Nero as he has become more skilled. Although it is ridiculous that Nero would know Vergil's attacks, it could have been made to hint that he really is Vergil's son.
As well as showing that Dante has learned from his fight with Vergil, and won't fall for the same trick twice.
Dante letting Nero keep Yamato; by most laws of inheritance, a deceased person's possessions go to any offspring before sibling. So as Vergil's son, Yamato rightfully belongs to Nero, not his brother Dante. Dante knows this and is just using It Was a Gift as a convenient excuse to give it to him; Nero's not quite ready to learn who his dad was and it avoids the subject for a while.
Many people wonder why Cerberus, a hellhound, is an ice elemental in 3. Anybody who has read Dante's Inferno (or at least studied up on it), however, would know that in the ninth circle, Satan was encased in ice. Another nod towards the epic, perhaps?
The third circle of Hell in The Divine Comedy where Cerberus is the guardian is mentioned to constantly be rained upon with cold, miserable slush. DMC's Cerberus may be a bigger reference to that.
And the level on which the fight against Cerberus takes place? Level number 3.
A bit of a meta-example, and may also be a bit of a stretch, as it was one of the things responsible for 2's much weaker reception. Why is this game easier than the others? Because it's the second latest in the series' Anachronic Order, and Dante has taken several levels in badass by then, making the enemies in 2 weaker in comparison. The game's easier because Dante is just that powerful now.
That also explains Dante's Awakening and its Nintendo Hard difficulty (at least its original release); since it was Dante's first major adventure.
One peculiar trait of Nero in 4 is that he swings Red Queen around with just his left hand for a majority of his attacks. It seems like a pretty odd way to make him distinct from Dante. However, it may have served as a subtle connection to another character. Earlier in 3, Vergil is shown wielding another BFS of the series, Force Edge, with one hand. Considering that Nero seems very similar to Vergil, perhaps this was done to further establish some relationship between them.
There's also the fact that his right hand started in a sling and ended up a demonic claw, he might just be using his left hand to swing Red Queen and fire Blue Rose since it's still human and easier to use them.
It gets even better on the few occasions Nero wields both Red Queen and Yamato at the same time. What other character in the franchise has been shown to use a similar combat style?
With all those actions Dante got and Sparda being left in the backstory, it seems that another game that stars Sparda would be fitting. However, you don't need Sparda as a main character. You're already retelling his tale through his legacy, especially if you use his costume.
Whether this was an intentional Shout-Out to Classical Mythology or not is unknown, but the Nobodies from the first game are among the most difficult and/or annoying enemies to deal with. Does anyone know what alias Odysseus goes by in the Odyssey when he and his crew are up against and stab the Cyclops in the eye? "Nohbdy", which coincidently in English is pronounced and has the same meaning as "Nobody", albeit they differ in that they are brutish rather than clever.
All bosses in 3 possess a Logical Weakness. Agni and Cerberus are weak against each other, for instance. A notable exception occurs during Dante's campaign, as none of his weapons deal extra damage against Beowulf. Vergil does not have that difficulty, as Yamato's darkness counters Beowulf's light. That explains his quick end by Vergil's hand.
In the form of an Author's Saving Throw. There has been some speculation by fans as to why Dante is more sober and serious in 2, with one popular theory is that Trish and Lady (though the latter was not conceived yet) were killed or faced some other unfortunate fate and that he blames himself for that tragedy. Actually, if one recalls the events of the 2 prequel novel, he did experience a depressing loss in that he killed a Trish from an parallel universe who served and remained loyal to Mundus despite his efforts to convince her to change sides. It was stated the novel that Dante lamented having to go through with it.
With the release of new supplemental material and Word of God in the lead up to 5, Dante's demeanor in the anime and 2 makes even more sense. The new timeline order is 3 > 1 > anime > 2 > 4 > 5. Now what happened in 1 that could've made Dante so depressive? He had just encountered his brother for the first time in a decade only to find him brainwashed by the demon who had their mother killed and was forced to put him down. Note that he seems to return to his 3-style persona in 4 after meeting Nero—it's because he realizes he still has family that he starts to cheer up.
This also re-contextualizes the entire tutorial battle. Here's Dante jumping in and "killing" the head of a clergy, eerie and antagonistic without even so much as uttering a word, when some young upstart with anger problems gears up to start fighting him without even remotely having a beat on Dante. Then the Red Right Hand of the Devil Bringer comes out, and Dante finally starts talking - that was the realization point for Dante, who goes from apathetically humoring Nero to indulging in a bit more of his flashiness shortly thereafter. The fact that Nero's own habit for showboating plays off of him only accentuates this.
At first glance Vergil, who is established as being an honorable Anti-Villain, stabbing Dante through his chest would seem as utterly lazy if not terrible writing in seeming to inexplicably turn Vergilinto something of aCard-Carrying Villain out of nowhere. However when one considers that Vergil and Dante are well aware of their partly Demonic heritage, of which includes the benefit of Healing Factor, it would be obvious that Vergil would know that he wouldn't be able to kill Dante that easily and pierced him just to keep him down so he could leave with Dante's half of the Perfect Amulet and likely wanted to force Dante to awaken his Devil Trigger powers to help him survivein the new worldhe wishes to establish (via recreating the Kingdom of Sparda).
The games have generally established the idea that using a Devil Arm requires the user to be able to dominate the demon in some form. Alastor and Ifrit in 1 attacked and possibly tried possessing Dante when he came across their Devil Arm forms. The bosses in 3 seem to admit their loss to Dante, and offer their power to him. The one exception is Beowolf, whose soul/power is converted into melee armor by Vergil after failing to kill him. Nero continues this trend despite not being able to convert demons into Devil Arms. Most of his abilities for the Devil Bringer are gained by absorbing remnants of defeated bosses or the alchemically powered relics he comes across. This difference between what Nero can do, and what Dante has been shown to do, could be explained by the gap in power and experience between them.
It's kind of brilliant how the three each have different demonic forms based on their interpretation of Sparda. Credo and Agnus both see him as a holy savior so they have light colors, and while Credo takes a purely angelic form as he sees Sparda as an Ascended Demon, Agnus' takes an insectoid form similar to how Sparda's wings actually looked. Compare and contrast Sanctus, who fully acknowledges that Sparda is a demon and grows horns for the final boss fight.
Vergil never lost Beowulf to Dante. Unlike every other Devil Arm in 3 Dante doesn't get a cut-scene for getting it. Second unlike Force Edge when using the Corrupted Vergil costumes Devil Trigger form of Nelo Angelo he can still use it. Finally Nelo Angelo in first game is said in the file to generate light when charging his attacks.
The reason for Dante and Vergil's Devil Triggers changing appearances depending on the Devil Arms equipped in both 1 and 3, as well Nero's incomplete DT in 4, could be attributed to them still being young and not quite fully grasping their powers yet. As The4thSnake points out in his video, the change in forms could point at the progression of Dante's power, where Dante finally settles in to his demon powers after defeating Mundus in 1 and thus his DT doesn't change in 2, 4, and 5. It's not until he overcomes his final mental hurdle in 5 that he unlocks his Sin DT. Vergil's DT changes between equipping Yamato and Beowulf in 3 and 4SE, but with Force Edge being the sealed form of Demon Sword Sparda, his DT is the default one. Nero's right arm in 4 could be explained that it was "locked" into Trigger due to the injury prior to the game alongside his desire to protect Kyrie. Yamato's acquisition awakens his demon power and influences his DT to being a manifestation of his soul/power because of the physical DT "lock" of his right arm. It's not until 5 where Nero fully grows into his own demon power, first seen through regrowing his right arm after Vergil ripped it off, and doesn't have to rely on any external influence to completely enter or exit his real Trigger, in large part due to his newfound storge love towards Dante and Vergil and past storge love towards Credo and Kyrie.
The series' Central Theme about how one's humanity is a source of strength not weakness is displayed in Lucia's battles with Arius in 2. When Lucia first fights Arius, she has recently learned she is one of his artificially created demons and is terrified she will become a threat to the people she is supposed to be protecting. When Arius defeats her she even tries to goad him into killing her. When Lucia fights Arius a second time she has reconciled with her origins while Arius has returned as a crazed demon. Lucia is at her strongest when she views herself as a person instead of a puppet Arius created whereas Arius sacrifices his intelligence and versatile magic for demonic power he has no control over and thus is defeated.
Arius is able to tell Lucia apart from the other Secretary demons despite her looking exactly like them. This ironically shows that Lucia is more human than she thinks as even Arius can tell the difference between her and the other artificially created demons who look like her.
A Nelo Angelo, Vergil's appearance resembles Sparda's demon form. This is a symbolic of how Vergil tried to emulate his father but failed, becoming a mindless slave instead of a feared and respected demon. Given it was Mundus who turned him into Nelo Angelo, it makes sense he'd subject Vergil to such a cruel punishment.
In 3 Lady, after being caught by Dante as she was falling from the tower, shoots him in the head. Moments later he leans back, showing no reaction to the damage, and she muses that this means Dante's a demon, too. She couldn't have had any reason to suspect it before that moment—everything she's seen him do is within her own abilities. What exactly would she have done if he had died from that, mourned her murder of a human? Does she make a habit of randomly shooting other people who are killing demons to see if they're secretly demons?
She saw ride a rocket like surfboard earlier. HOW in the hell would you consider Dante human after that?
First, Lady herself often exhibits skills and abilities that normal humans tend to be incapable of (e.g., rocket jumps). And second, that just raises more questions! Dante rode that rocket like a surfboard AFTER she shot it at him. So, either she assumed he was a demon all along and it was a stupid line on her part or she assumed that the guy fighting demons (in other words, the exact same thing she is doing) was a human, but she shot him anyway. He's not threatening her and she doesn't even see him attack a demon until later. As far as she is concerned, he could just be some guy standing in the wrong place at the wrong time, with odd hair.
Lady probably just thought anyone else hanging out at the Temen-Ni-Gru was up to no good, assumed Dante was a demon in human guise (the Inferred Holocaust of the surrounding town probably fed into this idea), had it confirmed to her in a sense when she shot him, commented on it to herself and continued her crusade. She displays a little Fantastic Racism towards demons, though Character Development lets her get over it.
She may have just been muttering a fact to herself after the moment had passed. Much like how someone might say "Well, that happened" or something similar when witnessing or experiencing something that they don't really have time to fully process or comment on in the moment.