Due to the wide variety of classes available to one in Pathfinder, there are quite a lot of options for making a Necromancer, and each approaches the concept with its own flavor. Below are listed the class options for making black-magic or undead-focused characters.
Dirge Bard: This class plays to a more charismatic and debuff-focused necromancer, limited to the bard’s spell list. The Dirge is all about invoking fear and playing mind-games, but they lose their versatile performance, jack-of-all-trades, well-versed, and lore master abilities. Their shining ability (in flavor, not usefulness) is in raising the dead during a bardic performance, but the reanimated corpses only last for as long as the performance does.
Undead Lord: In a world of necromancers, the Undead Lord cleric archetype is almost top-dog when it comes to controlling the undead. They only get access to one domain (Undead) but gain a slew of awesome abilities for managing your rotting minions in the process. Combined with the Undeath variant channeling, you’ll also be healing your minions 1.5x more than usual. This one is a favorite.
Witchguard: The ranger has an unexpected ability to be a competent fighter with a hint of necromancy in the way of the Witchguard archetype. This variant gives the ranger the ability to select a witch’s patron and cast the first four spells from the patron spell list. As such, if you choose Plague as your patron, you will gain access to the bread-and-butter of undead control: Command Undead and Animate Dead. Unfortunately, the Witchguard won’t get animate dead until 13th level, but a wand will suffice until then.
Sorcerer Bloodlines – Pestilence and Undead: Since the sorcerer’s archetypes alter the base class more mechanically than thematically, we have to turn to the sorcerer’s many bloodlines for our necromancy. Two bloodlines stand out in this regard and really define the two halves a good necromancer. The Undead bloodline, as you can imagine, governs the creation and controlling of undead with a hint of battlefield control. The Pestilence bloodline carries all of the debuffs, and you will be able to create undead through the use of sorcerer spells. If you’re feeling saucy, you can even go as a Crossblooded sorcerer and carry both bloodlines for maximum evil.
Wizard: The wizard is one of the most iconic classes to go necromancer with, and it shows in how little you have to change to get to that point. Pick up necromancy as your specialized school and nab some spells that are tooled towards the idea. You could go further into the zombie master concept by picking the subschool of undead. Because of the ease of getting into necromancy, you can go into the few archetypes wizard has quite easily, becoming a gun-toting necromancer if you so wish.
Reanimator: The alchemist has with him an interesting archetype in the Reanimator, a Dr. Frankenstein of types who can use his alchemy to raise the dead. He can only make zombies at 7th level, but it does not set a limit to how many zombies can be under his control. At 13th level, he is allowed to use the Create Undead spell, but the undead created are not under his control. He does not have a way to control undead, either, so this poses a problem. Nonetheless, the Reanimator is a very cool (if lackluster) option for aspiring necromancers.
Still to come: Inquisitor, Magus, Oracle, Summoner, Witch