User blog comment:KillRoy231/Big Bads of Angel/@comment-4199083-20140109094057

Angel follows a slightly different style of story formating than Buffy does. While each season of Buffy tends to have the main story arc begining from episode one to episode twenty two (Buffy's main antagonists also worked in this fashion), Angel had storylines being resolved mid-season and crossing over seasons (seasons two, three and four in particular). In Angel, Wolfram & Hart are the arch enemies for the whole series while all other main threats are connected to it some way or another.

Season 1 - Wolfram & Hart. The Senior Partners are in charge of W&H, Lindsey and Lilah are lawyers working their way up the ladder and Holland Manners is their supervisior.

Season 2 - First W&H then Darla.

Season 3 - Daniel Holtz and Sahjhan.

Season 4 - The Beast who turns out to be the Little Bad when the Big Bad was truely Jasmine.

Season 5 - All in all, it's the Senior Partners, but Circle of the Black Thorn was simply the only enemy A.I. could take down and make a big impact.