Angels of Absolution
The Angels of Absolution are a second founding successor chapter of the Dark Angels and perhaps the successor with it's head on the most straight since they realize that the sins of their forebearers are not their own and thus they don't have to seek out forgiveness from the Emperor; that doesn't mean they don't join in a merry game of 'Hunt the Fallen' once in a while.
The A of A are for the most part similar in temperament, outlook and everything else to their parent chapter; it is just on the one belief that they (quite sensibly) differ; they believe the actions of their forebearers in combatting the corrupted angels during the Fall cleansed their blood of the guilt and that their many acts in the Emperor's name since then have only confirmed that. Considering they are talking about 10,000 years here you can see where they are coming from. Just how many oceans of blood does the Emperor need to wash that much guilt off, damn?
They don't yet have the balls to tell their parent chapter to man up and stop being so emo about the whole fallen thing.
Unlike a number of successor chapters, they have a number of mentions of campaigns they have undertook, given them some colour and personality.