As Iscariot's "trump card", he is the single greatest warrior the Vatican can bring to bear. Alucard noted that he was the only one who he'd let defeat him (in accordance to Alucard's own belief that only a man can slay a monster).
In battle, Alexander Anderson uses scores of blessed bayonets presumably made of silver as well as smaller blades which are held between his fingers like claws. He wields the bayonets in close-combat (one in each hand) like swords and can also throw them with alarming accuracy (especially considering that he often throws the bayonets in large numbers, usually holding them between his fingers). It is possible that Anderson can control the bayonet's trajectory after he throws them, ensuring that they hit their target. An example of this is in OVA I when Anderson was able to impale Seras with multiple bayonets, while walking down the stairs from the upper level which was around the corner of the hallway. Some of the bayonets are shown to have hand guards in the manga and TV series. The type of he uses most appear to be Austrian sword bayonets, with custom hand grips for an easier hold.
Anderson can also throw bayonets at alarming speeds, enough to cause sonic booms and shatter windows.
The power of the bayonets against vampires seem to vary. In Volume 1, the bayonets irritate and sting vampires, but in Volume 6 they are so powerful that vampires literally crumble around them. One possible explanation for this would be that he never stabbed Seras Victoria in the heart when he attacked her in Volume 1, as he wanted to enjoy his "hunt." Seras was severely wounded and kept from regenerating but she could not be killed unless her heart was pierced; so Anderson may have simply stabbed the vampires in Volume 6 right through the heart in order to kill them quickly rather than just wound them like Seras. Another explanation would be that Anderson is simply equipped with more powerful bayonets by Iscariot for more dangerous situations.
Anderson may also have different types of bayonets for sertan situations, for instance in volume 8 he hurls a chain of bayonets that seems to explode and destroy swarms of Alucard's familiars in an instant. In OVA VIII, Anderson calls this device the Exploding Chain (爆導鎖, Bakutōsa; literally translated as "Blasting Sword Chain" in the original Japanese dub).
Oddly enough, he never showed any limit to the size of bayonets that he can pull out of his coat, as he has some that are smaller than daggers and others that are bigger than swords. Strangely it's s never been said how many bayonets he can throw or pull out his coat and sleeves, which also, doesn't show any sign of pockets or hilts keeping the blades. This can be seen as in most fights, where his coat waves madly in the wind or in fast movements, showing clear sign of its inner sides. Whether he can summon an endless number of bayonets, they are concealed with some sort of holy power or can be generated by nano-technology in his clothing remains unknown. Hirano claims something among the lines of Anderson being '4th-dimensional.
Superhuman Strength and Speed
Anderson possesses extraordinary strength, speed, and reflexes, far above what is considered normal for a human. He also possesses a great deal of dexterity (as he can skillfully wield bayonets easily in either hand), agility, coordination, balance and stamina. In the anime, Anderson slices a subway car in two using only his bayonets. In the manga and OVA series he has fought Alucard (who literally has the strength of a billion people) to a standstill with his bare hands, and had enough strength to throw his bayonets through a tektite composite in order to allow the Level 0 souls summoned by Alucard to break through Maxwell's protective cabin. Anderson's physical strength is immense, being able to stagger a being such as Alucard with a single punch; especially considering Alucard takes high caliber bullets to the chest standing up and is unfazed.
Anderson can easily throw bayonets with enough force to pierce human skulls and, as shown in the TV series, can cut through a subway train with little effort. His speed and reflexes are sufficient enough to dodge bullets (not that he would need to thanks to his regeneration), cut threw people so quickly that it doesn't even look like he's moving and take even Alucard by surprise. It is unknown if these abilities are a byproduct of his regeneration or are some other form of artificial enhancement. Anderson's skills, like Walter's, may simply be a combination of natural skill and years of fighting experience against supernatural foes (during their final fight, Alucard states how impressed he is with how Anderson had kept his body in top fighting condition for so long, which is similar to how Walter has maintained most of his incredible skills even in old age). It is also likely, however, that Anderson's strength and speed are a result of bio-technological treatment in order to make him more equal to the vampires he hunts, as Integra notes when she locks swords with him in Northern Ireland.
Holy Barriers and Consecration
Anderson was capable of using small bayonets in the TV series to affix pages of scripture onto the walls of a building, in order to "purify" the house and prevent any usage of black magic. In the manga and OVA, this ability is referred to as a "barrier," the pages are stapled to walls using nails and act more like a ward against vampires. Seras, specifically, could not escape through a door or window blocked by this barrier. Anderson can also use Bible pages to teleport, though how far he can travel has not been made official. In the TV series, Anderson was also shown to use Bible pages in order to trap Alucard. Specifically, he used them to entangle Alucard's arms before slicing his head off.
Father Anderson is a "Regenerator," meaning that he is able to restore body parts that are lost and heal himself. This is clearly demonstrated in Episode 3 of the anime; Alucard's bullet enters Anderson's head, but he recovers quickly and appears unscathed. This has raised some confusion over why Anderson retains the scar on his left cheek. The most likely explanation is that he received the scar before he received his regeneration ability (he was also shown in a flashback in the TV series without the scar, further proof of this). Thanks to his enhanced healing and durability, Anderson is almost completely indestructible. He is able to shrug off automatic-gunfire from multiple simultaneously firing weapons (none of which even pierce his flesh), and even Alucard's explosive silver bullets fired from the casull. This gun along with many other mystical weapons are the only known weapons that can actually harm him, this may mean that Anderson may have a weakness to magic. His clothes also appear to be able regenerate, as they're seen getting torn up but then back to normal in the next seen this may be the reason why he has unlimited bayonets in his coat because the are made by nanotechnology.
Anderson claims that his ability is "the divine gift of God," but later states that it is due to "man's technology." In the manga he calls it a "technique" while Integra calls it bio-technological regeneration (possibly some form of nanotechnology meaning he is cybernetically altered, this would make sense considering he is often called a "cyborg"). In certain adaptations, Integra claims Anderson's regenerative powers surpass any known nanotechnology, possibly being divine. Anderson is often considered not entirely human due to this augmentation , and Integra goes so far as to call him a "thing" or a "monster" while in the TV series Alucard states that Anderson is less than human and a "failed science experiment." Still, in the manga and OVA it appears that Alucard considered Anderson human enough to fight monsters (Alucard believes that only humans can destroy "monsters" like himself) because Anderson never sacrificed his humanity when he became a "Regenerator", Anderson never sacrificed his humanity. This is shown when Alucard becomes enraged at Anderson for choosing to use the Nail of Helena on himself, truly becoming a "monster" rather than a man.
Though much stronger than the regeneration of most vampires and sometimes even Alucard (depending on which level he's using), Anderson's healing factor is not without its limits. Using the Jackal, which was specifically designed for use against strong regenerators like Anderson, Alucard is able to shoot out a chunk of Anderson's arm which doesn't seem to be able to regenerate. A similar event occurred in the original TV series, during a battle in a subway. Alucard shoots off both of Anderson's arms with the Jackal and they don't regenerate (or regenerates much slower than usual). Anderson is forced to flee, and he is not seen again until the final episode where he is in a crowd watching Alucard fight Incognito. At this point, his arms have been restored (meaning the Jackal may be able to temporarily negate the healing of regenerators).
Anderson's eventual demise comes when Alucard rips out Anderson's heart, which is pierced with Helena's Nail. Alucard stated mid-way in their fight that destroying the heart is the only way to kill monsters like themselves. It appears that Anderson's healing, like his bayonets, can be "upgraded" by Iscariot (in the OVA, Integra mentions that Anderson's healing has been upgraded when they first meet, meaning that it is better than what she had previously heard or seen ) for more challenging situations, much like Alucard.
The Nail of Helena
Alexander Anderson receives "Helena's Nail" from Section III Matthew, the Vatican's relic retrieval division. Discovered by Helena, Constantine's mother, it is said to be one of the nails of the True Cross. In fact, in the dub, Alucard remarks with hostility that the nail smells 'of blood and miracle.' Anderson stabs himself in the heart with it and he became, in the words of Alucard, 'one of God's monsters.' He also said that he turned himself into 'a scrap of miracle' using a 'scrap of miracle.'
Anderson displayed some peculiar plant-related powers, and has shown himself to be powerful enough to stop the Jackal's bullets with his thorns. Also, it appears Anderson's blades were now powerful enough to affect even Alucard's immortality. Anderson's regeneration seems to have been further enhanced, his body growing the same thorny vines where he was injured, and he was only killed when he had his heart, where the Nail had been driven, ripped out of him. In addition, these vines can wrap themselves around his foes and cause injury, and instantly ignite all things "unholy" or "satanic," causing them to erupt in flames. Anderson's face and likely all of his fleshy body were transformed into a humanoid mass of thorny vines. Alucard noted a relationship between these thorns and Christ's Crown of Thorns.
The use of the Nail prompted Alucard to officially label Anderson a monster rather than a human. Alucardstates that the monster who acknowledges God is no different than a monster who doesn't, they are both one in the same: monsters. Alucard would have been proud to die at the hands of a human, but Anderson was no longer human after the Nail was embedded into his heart so he had to be destroyed like any other monster.