Whilst Liam is human and Angelus is a vampire, Angel is a third, unique persona, a demon burdened with a human soul. A hybrid of man and vampire, he constantly deals with vampiric urges, and the human conscience that prevents him from ever forgetting his past misdeeds. Though the early seasons of Buffy expressed the view that when a human becomes a vampire, "You die, and a demon sets up shop in your old home; it walks like you and it talks like you - but it's not you" ("Lie to Me"), later seasons of Buffy and Angel had the relationship between Angelus and Angel far more intertwined. Angelus once referred to himself as "Angel" during Season Two of Buffy (possibly to torment Buffy). Angel usually says "I" when speaking of Angelus, but has also used "he". In "Amends" Angel protests, "It wasn't me!", but more often speaks of Angelus' crimes as his own. They share the same memories, and Angel never resumed the name of his human original, Liam (except while amnesiac in "Spin the Bottle"). Also, in Season One's "Eternity", Angel reverts back to his evil self without even losing his soul, when he is drugged and enters a state of 'bliss' that allows Angelus to regain control. This suggests that in a subconscious state that Angel's true nature is allowed to appear, although it may have been that the drug-induced state of bliss 'tricked' Angel's body into thinking that the curse had been broken.

Angel: Look, I'm weak. I've never been anything else. It's not the demon in me that needs killing, Buffy. It's the man.

(Episode 3.10 (Buffy) "Amends")

Angel: ...there is no guilt, there is no torment, no consequences... It's pure. I remember what that was like. Sometimes I miss that clarity.

Cordelia: But not the trying to kill your friends and family part, right? Just checking!

(Episode 1.21 "Blind Date")

Cordelia (possessed by Jasmine): What I remember when I was a higher being... I remember seeing you. Your past. When you were Angelus.

Angel: I've never tried to hide who I was. Or what I've done. You already knew.

Cordelia (possessed by Jasmine): Knowing's different than living it. When I was up there, I could look back and see everything you did as Angelus. More than see. I felt it. Not just their fear and pain. I felt you. And how much you enjoyed making them suffer...

(Episode 4.07 "Apocalypse, Nowish" Note: Since the above was said by the entity that would become known as Jasmine while posing as Cordelia, this specific example of Angel being just a different aspect of Angelus comes from a questionable source to say the least.)

Angelus' cunning and cruel nature makes him exceptionally lethal.

The relationship between Angel and Angelus has been described and depicted in numerous ways. Both personas are shown battling for control inside Angel's mind in the episode "Orpheus". In Season Four, Jasmine threatens Angelus by telling him that she will lock him away inside Angel forever, where he will be forever watching, forever thirsty, forever longing to escape his prison. When the two confront each other in "Orpheus", they clearly appear to be different people, albeit evenly matched. Though Angelus does not accept that Angel is truly 'seperate' from him (believing that Angel is merely "denying what he is"), he nonetheless draws a line between the two of them, and is disgusted with what Angel does with his body while in control. Angelus particularly resents Angel's two decades of eating rats after an incident he we succumbed to temptation and bit into from a murder victim. As seen in "Becoming, Part One" and "Becoming, Part Two", it takes a few moments for Angel to remember the events of Angelus' life after the curse comes into effect. This gap in memory is presumably the reason why the spell that erased all memories and references to The Beast did not affect the part of Angel's mind that Angelus resides in.

Although Angelus' bodycount was vast, his worst weapon was arguably his boundless cruelty and love of psychological intimidation. He is prone to brutal displays of what he would see as affection, one such incident involved him nailing a puppy to a wall, though a full explanation of this was never given as Buffy interrupted Giles with "Skip it, I don't have a puppy. So skip it." Another example of Angelus' grisly acts of love was when he brought Dru a still-warm human heart on Valentine's Day. Angelus has always had an obsession with elevating death to an art form; a truly satisfying kill must be perfectly framed and appreciated. He delights at the prospect of torturing a bound Giles in "Becoming, Part Two", mentioning that that the last time he tortured someone, they hadn't even invented the chainsaw. In the episode "Amends", The First Evil references him killing a man's three children, then propping them up in bed so that they appeared to be sleeping. It was only after the father kissed one of them good night that he felt how cold they were. This is mirrored in a prior episode when Angelus placed the recently-slain body of Jenny Calender in Giles' bed, making Giles believe she had set up a romantic evening for them.

Angelus had a weakness in that he was prone to excessive talking, and a need to utterly obliterate the mind of his victims before killing them. This streak of sadism sometimes gave potential victims time to escape or fight back (although it made little difference as he almost always got them in the end). Spike once observed to Angelus "you bloody well talk them to death before you kill them!"

It should be noted that Angelus is often referred to as 'Angel', the former typically being used to distinguish the two if necessary. Angelus accepts 'Angel' as a nickname, unwilling to see a distinction between his 'ensouled' half and his evil half.