I'll explain why. Demons and angels are stronger 'mentally' and 'physically' compared to human beings.
Okay, this is opinion, too. You can't really prove this statement, except that demons are obviously stronger in the DMCverse than humans, because we haven't seen anything yet referred to as an 'angel' in there that really was one. They have all been demons so far, or so the games tell us.
Yes, in the context of DMC, demons are strong. But do we have an angel to examine and compare with? Not yet...
You can assume it, based on the likelihood that supernatural beings are superior to humans in that universe, but you can't claim nobody can contest your theory when you can't prove your own by canon. It's a supposition, so it's equal to everyone else's theories that exist outside of the canon.
With this said, it's understandable why Dante is so powerful. I've always thought how it didn't make much sense that Dante would age like a human does, but he doesn't get hurt like a human does.
If he's part angel and demon with no human in there, it doesn't make sense he'd age at a human rate either, does it? Sparda lived for over 2000 years. If there are angels, it wouldn't be a stretch to imagine they have longer-than-human lifetimes. So where does Dante get his normal human ageing without human heritage?
Sure, he gets battered around. Take Nero kicking his ass at the beginning of Devil May Cry 4 for example. Dante's demonic powers crackle and he wakes up again from his knocked out/unconscious state of mind. Nero nearly served Dante a can of whoop-ass (In fact, he basically did) Dante's human side wouldn't be able to heal itself quickly. He may have Sparda's blood within him, but how does he harness it so well?
It seems like it kicks in like a survival mechanism; he doesn't harness it until he's in danger. A bit like in humans where adenaline and fight-or-flight instinct can sometimes affect strength when you sense your life is in danger, making you run faster, hit harder, and do things you wouldn't be able to under normal circumstances.
With that said and in mind, Dante should have to wait (Be inactive from battle) before his demonic strength inside him can heal his wounds. When does Dante sit back and have a break? He does not. He jumps into all these events, gets knocked around, but never gets any real damage dealt to him.
Well, he is rendered inactive: Alastor incapacitated him for a short while, having a huge stone sword in him did for a short while, Yamato and then rebellion being shoved through him also incapacitated him, and Force Edge briefly. If you're talking about the length of time out of the battle for Dante being seconds rather than hours or days, we could chalk it up to the fact he's not a mere vampire, but the son of a demon so powerful it could beat the Underworld's Emperor. Seems like these are the qualities bestowed on Dante by that heritage. (But we are arguing here something that can't be argued in real terms, these are the game's own 'laws of nature'.)
Other examples. Dante's wounds against Vergil. I know Vergil awakens Dante's Devil Trigger, but he would of still be weak after that battle I'd imagine. Trish attacking Dante at the beginning of Devil May Cry 1. Dante seems unscathed by the attacks. Alastor going into Dante (Dante proves he is powerful enough to handle the sword) this is because the sword does not seem to hurt him at all. Fighting Mundus. Dante gets hit by Mundus when he confronts him for the first time, and he heals right after (He must do, because you go straight into the Boss battle after that scene).
You could still chalk that up to the influence of demonic power awakening under duress. We don't know the ins and outs of DMC's demonic power, so we can only observe and make judgements based on what we're shown by the game - that is, when it awakens, it's pretty damn powerful, and seems to prevent death at pivotal moments. What we are shown isn't entirely congruous through the series either. Now for Dante to be referred to as even more powerful than Sparda doesn't make sense, but if he's half angelic, why does he bleed and age like a human? (I don't think the people who made the games were looking as hard as we are at the whole thing, lol).
Demons are not immortal in the series, obv. Vergil is defeated (as Nelo), Mundus is beaten, and Dante fights and destroys plenty of them throughout the series. You have to accept that Dante is only 'immortal' and wins all the time because he's the main character in a game that wouldn't exist if he didn't.
Every time Dante has ever gotten hit by anything, he amends himself almost instantaneously. Unless Dante was more powerful to begin with (For instance, a full demon) then I've never been able to understand how he has always been so powerful. Vergil on the other hand does not seem to possess this strength, or the strength to continue fighting if he is weak. Let's examine Dante's Majin form in Devil May Cry 2. Dante's desperation Devil Trigger. Dante has the will to still be so strong even when he is meant to be so weak. His desperation Devil Trigger clearly shows this.
If Vergil is his twin, how can he not also possess the same power Dante does? Angelic qualities if you're arguing them? He must do, unless he is not really Dante's twin, but the canon and the evidence states that he is, so he should possess this overwhelming power too. Instead I'd suggest Vergil's weakness at the end was a result not of a failure of strength only but also perhaps of his philosophy and hopes. Dante may have demoralised him too, with some of the things he said at that point. Morale goes a long way in a battle.
But of course story-wise, Vergil had to lose. They never really explain why Vergil loses to Dante when they should be evenly matched, but in any case, he was doomed to failure. (Personally I fancy that Vergil lost because his style is dependent on having the upper hand, on attacking rather than defending. Vergil's 'strength' is in attacking so fast and precisely the enemy is dead before he knows it, but Dante is like a bulldog that doesn't quit. This style of fighting and being at the same time more robust than the average enemy would logically eventually wear down a limited and aesthetic style like Vergil's.)
Realistically, as I said before, Dante would suffer way too much with his human side getting in the way. I'm not doubting he can't be strong and everything even with his human form. I'm simply saying that if he was half demon and half angel then it'd make more sense as to why he can take such a heavy amount of damage and then just shrug it off.
I somewhat agree, but I don't think the character and game designers really cared in the beginning about making Dante in any way realistic.
It would make more sense that Dante's demonic powers are always active, for him to survive massive injury as he does. But it seems that most of the time, they're dormant, or...
...his flesh and bones are 'different' than that of a normal human. Remember when he attempted to punch Vergil in the face and Yamato stopped it, apparently because Dante's hand bones met the blade? If that's a demonic weapon that
can cut through stone and bone like butter, then Dante's bones must be harder than steel. Same when Beowulf punched him
into the ground. He has to be made of something stronger than normal flesh not to have become a splat. So injuries that would mince a human are not fatal to him although they do cause pain - and that special flesh could validly be demonic as much as angelic.
The games have Dante rely on mainly Devil Arms and his mystically-enhanced guns against demons, rather than normal weapons, which implies 'higher demon's' flesh is much tougher than human flesh, or else Devil Arms are just far more efficient against them. (He didn't take on the Underworld with a shotgun and a nail bat). So Dante's demonic heritage can certainly account for his high physical toughness compared to the average human. Whatever he's made from, it's not 'normal' human flesh.