What alignment would you associate with each class

[Theodoxus]

I think the three PHB Paladin oaths map nicely to the three good alignments. Devotion - Lawful Good, Ancients - Neutral Good, Vengeance - Chaotic Good. It felt like a nice compromise between strictly pigeonholing the Paladin into Lawful Good, but still keeping Paladins = Good as important fluff. Conquest paladin (or the "I do whatever the *** I want Paladin, as I call it to my friends) is when they went off the rails for me.

TBH, my gut feeling is that all of the Paladin classes probably ought to be played as Lawful something or Something Lawful, but as I read through the Ancients Paladin Oath the first few times, I got the feeling that it didn't have to be Lawful to work.

EDIT:
Oh ... and what Trask said. Missed seeing that before I answered.

Vengeance always had a chaotic neutral flare to me. So, maybe Chaotic Neutral with Good tendencies? (to really call back ideas that are NOT at all present in 5E).

@OP, Monster Slayer feels Neutral as a baseline, and then depending on what they concentrate on, add an ordinal. So, anti-Undead or Fiend is probably NG. Anti-monstrosity is probably TN or LN. Anti-metallic dragon, NE; anti-chromatic dragon, NG; anti-abomination, NG all the way to LG depending.