DISCLAIMER: I do not own Devil May Cry or Hellsing.
Alucard and Vergil faced each other, Alucard with his guns, Vergil with Yamato.
"Vergil Sparda, you are a fool for attacking me."
Vergil smiled slightly, though there was no humour nor warmth in his face.
"Am I now? I know of your ability to regenerate, Count. You fail to understand that I can kill you anyway."
Alucard smiled, showing all of his pointed teeth.
"Oh, can you?"
Vergil approached slowly.
"The demon lord Abigail. He had regeneration just like yours, and Dante killed him easily by using his devilish power to directly obliterate Abigail's soul. If Dante did it, I can do it too!"
Before Vergil had even finished speaking, Alucard had begun laughing. By the time Vergil was finished, the laughter had progressed to maniacal howling. Alucard found Vergil's arrogance and presumption of equality to Dante very amusing.
"You truly think you can do it just because Dante can? You foolish creature."
Vergil glared at Alucard, furious. "Shut up."
Vergil charged at Alucard, slashing him through. Vergil then created a series of dimensional cuts which reduced Alucard to a burst of blood. The blood then reformed into Alucard, and he laughed again. Vergil charged into Alucard full force, morphing into his devil form and releasing the full magnitude of his power. Alucard took Vergil's sword square through the heart, and felt the devilish power eating at him.
There was an explosion of blue energy which engulfed the entire rooftop, blue bolts of electricity arcing across it. In the centre of the explosion, Vergil's blue devil form stood, the blast of devilish power obliterating Alucard, wiping the vampire king into nothing.
Vergil fazed back to his human form, feeling slightly drained. He searched for Alucard's soul, so as to turn it into a weapon, but he could not sense it. Vergil disdainfully turned away, ready to leave.
"Pathetic."
Just as Vergil was about to leave, he heard Alucard laughing. He readied Yamato, but Alucard was nowhere to be seen.
Alucard's disembodied voice said, "You are a total fool, Vergil Sparda. I am familiar with the demon Abigail. In fact, it was his regeneration that gave me a pinnacle for my own. While Dante is indeed capable of destroying me, you are not worthy, as you are only a monster yourself. You and Dante were born halfway between monster and man, but each of you, through sheer effort, has made themself more one than the other. Dante is one who fought to become a man, while you fought to be a monster. Each of you has achieved your intention, and behold the magnitude by which he is your superior. I would in fact be proud to die by Dante's hand, but you are a degenerate monster."
Alucard reformed in front of Vergil, smirking.
"You may believe you are equal to Dante, but he is a million times your superior. Perhaps a billion even, or a trillion. You dare to call yourself his twin brother?"
Vergil charged and started attacking, but Alucard reformed each time he was vivisected.
"Control restrictions 3…2…1… Released!"
Alucard formed into a creature composed of shadow, while Vergil morphed into his devil form again.
"It is useless to fight me, Vergil Sparda! Only a man, such as Dante, can destroy a monster such as me. A monster such as you could never destroy me, as you are even more wretched than I!"
The two monsters slammed together, swords and shadow tendrils slashing. Vergil was still far stronger physically, but any damage he did instantly healed, and for all his power, he could not directly attack Alucard's soul as Dante had directly attacked Abigail's. Vergil simply wasn't capable of such a thing.
Dante threw open the door to the roof, Seras close behind him. In front of them stood Alucard, back in his human form, who held the unconscious form of Vergil in his hand.
"Look what I just caught! I just caught Dante's little brother out past his bed time."
Alucard tossed Vergil onto the shredded rooftop, and Dante picked Vergil up.
"Let's see if big bro has any useful information. Thanks for not killing him, Alucard. I'll bet it was tempting. He was always a pain in the ass."