Assassin as Archetype?

[Slayer Lord]

So I've been thinking a bit how to play an assassin in Pathfinder, but neither this game nor 3.5's version is all that great. But what if one were to replace the PrC entirely with an archetype? Maybe for Unchained Rogue, or Ranger or something. Has this already been done somewhere? If not, could you provide some insight on how to make a functional one?

[Geddy2112]

Shadowy hitman killer is a concept, not a class. Most classes can be built to do this.

The slayer is a really good class for a non assassin assassin, and has several shadowy killer archetypes. If you wanna be a sniper, rogues and slayers both have a decent archetype to do so.

Alchemists and investigators can also do the job decently well, and prestige into the alchemist class better because they are intelligence based. A magus is also intelligence based and even better suited to one shot killing than the alchemist/investigator. Even a monk can do the job with the ability to stun/disable people in a single hit.

The death attack thing is not really seen anywhere else, but if you are sneaky and able to do enough damage in a single hit/round, who needs a fancy death attack?

[Florian]

Ninja and Slayer can pick up Assassinate as Advanced Tricks at 10th. Poison Use is a general Rogue Trick available to all three classes, as well as PrC.

I´d base it on a Slayer with some potential dipping into Daggermark Poisoner.

[Doctor Despair]

Just puttin' it out there that you can, with some cheese, get assassin as early as level 2 in 3.5 at least. :) I'm sure that broken nonsense doesn't function in Pathfinder though.

[Psyren]

Ninja and Slayer can pick up Assassinate as Advanced Tricks at 10th. Poison Use is a general Rogue Trick available to all three classes, as well as PrC.

I´d base it on a Slayer with some potential dipping into Daggermark Poisoner.

^ This - Slayer is pretty much the "Assassin as base class." You could also, as suggested, make an exceptionally stabby uRogue.

[Petrukio]

Poison Use is a general Rogue Trick available to all three classes

Just as a clarification, this is relatively new. The Slayer does have Poison Use as a Slayer Talent, the Ninja gets it automagically at first level, but Poison Use as a Rogue Talent has only recently appeared in Blood of Shadows. (It was intended for the Dirty Tricks Toolbox, but never actually showed up there.) Previously, it was only 3PP (Drop Dead Studios' Rogue Glory, to be specific), and only an advanced talent at that.