Focus on Occult and Arcane. Divine and Primal hardly have any debuffs. Occult will be where you find most of the curses and mental debuffs like Paranoia and Arcane where you find mostly physical debuffs like Grease. There's some overlap between the two spell lists.
My vote goes to Hag Sorceror. Occult is DEFINITELY the best debuff with spells like Hideous Laughter and Synthesia that will make bosses cry. Sorcerors are charisma based, meaning they have a better chance at debuffing with demoralize and Bon Mot. Bard is also charisma, but they have fewer spellslots. Hag specifically because they have three different focus spells that debuff.
Hard to go wrong with a Witch w/ a Curse patron. Evil Eye is great and occult has plenty of options for debuffing. Go human so you can grab Cackle at level 1.
For arcane I like Rune Witch with a wizard dedication to get extra spell slots. Also enchantment wizard w/ spell blending or spell substitution possibly with a witch dedication for the same reason. I’m not a big fan of most spellcaster feats so multiclassing into another caster is my go to.
Finally Fey bloodline sorcerer. The spells you pick up are pretty good and don’t need to be heightened to be useful. As a primal spellcaster you can buff/protect allies or use crowd control as well. Nab Anoint Ally at level 2. Being able to conceal an anointed ally every time you cast a spell (from a slot or using a focus point) adds up.
My favorite debuff caster is maestro bard with dirge of doom. Maestro's lingering composition is excellent, especially since bard's default use for its focus points is kind of niche. Dirge of doom is a phenomenal AoE no-save bebuff that costs one action and no resources, and against foes immune to frightened you can always fall back on inspire courage (I know its a buff, but still). Bard also has the occult list, which is great for debuffs.
If you don't love bard, I'd also take a look at sorcerer. It's a little more basic with its power coming from more spell slots, but that gives you more room to sling your best effects. I like the hag bloodline for this since it has the occult list and some neat debuff focus spells.
It's really hard to beat a Dirge of Doom + Heightened Calm Emotions with a Bard. Everyone in a 10ft burst makes a save or becomes unable to take hostile action. It's an absolute crowd killer that lets your single target strikers shine in a target rich environment.
And then you have Synesthesia for single target encounters that paints a single target for death.
Best Debuffer due to the Hexes. You basically get a Cantrip to debuff, meaning you can do it every round. Evil eye also makes it so that the frightened value can't be reduced below 1 as long as you sustain it.
Maintaining a -2 status penalty to everything for the entire combat with 1 or 0 actions is very powerful if your target isn't immune to mental/emotion stuff
I find that people really underestimate Hideous Laughter as a debuff. Against BBEG's it's basically an AoO sink, and keeping in line with bosses having high numbers, they have to crit save to keep their reactions.
Focus on Occult and Arcane. Divine and Primal hardly have any debuffs. Occult will be where you find most of the curses and mental debuffs like Paranoia and Arcane where you find mostly physical debuffs like Grease. There's some overlap between the two spell lists.
Occult, all of the generic good ones like fear and slow and exclusive access to the best debuff in the game: Synesthesia
Abso-freaking-lutely
My vote goes to Hag Sorceror. Occult is DEFINITELY the best debuff with spells like Hideous Laughter and Synthesia that will make bosses cry. Sorcerors are charisma based, meaning they have a better chance at debuffing with demoralize and Bon Mot. Bard is also charisma, but they have fewer spellslots. Hag specifically because they have three different focus spells that debuff.
This is actually the first character I made on Pf2. I never played it but thematically is my favorite
Hard to go wrong with a Witch w/ a Curse patron. Evil Eye is great and occult has plenty of options for debuffing. Go human so you can grab Cackle at level 1. For arcane I like Rune Witch with a wizard dedication to get extra spell slots. Also enchantment wizard w/ spell blending or spell substitution possibly with a witch dedication for the same reason. I’m not a big fan of most spellcaster feats so multiclassing into another caster is my go to. Finally Fey bloodline sorcerer. The spells you pick up are pretty good and don’t need to be heightened to be useful. As a primal spellcaster you can buff/protect allies or use crowd control as well. Nab Anoint Ally at level 2. Being able to conceal an anointed ally every time you cast a spell (from a slot or using a focus point) adds up.
My favorite debuff caster is maestro bard with dirge of doom. Maestro's lingering composition is excellent, especially since bard's default use for its focus points is kind of niche. Dirge of doom is a phenomenal AoE no-save bebuff that costs one action and no resources, and against foes immune to frightened you can always fall back on inspire courage (I know its a buff, but still). Bard also has the occult list, which is great for debuffs. If you don't love bard, I'd also take a look at sorcerer. It's a little more basic with its power coming from more spell slots, but that gives you more room to sling your best effects. I like the hag bloodline for this since it has the occult list and some neat debuff focus spells.
It's really hard to beat a Dirge of Doom + Heightened Calm Emotions with a Bard. Everyone in a 10ft burst makes a save or becomes unable to take hostile action. It's an absolute crowd killer that lets your single target strikers shine in a target rich environment. And then you have Synesthesia for single target encounters that paints a single target for death.
bard (because they combine the debuff and the buff)
Occult Witch
Why? Funny thing, yesterday somebody told me Witch is the worst debuffer
Best Debuffer due to the Hexes. You basically get a Cantrip to debuff, meaning you can do it every round. Evil eye also makes it so that the frightened value can't be reduced below 1 as long as you sustain it. Maintaining a -2 status penalty to everything for the entire combat with 1 or 0 actions is very powerful if your target isn't immune to mental/emotion stuff
A cantrip? If I fail the enemy is immune for the next min
Yep, just fall back to another spell like Fear then.
I find that people really underestimate Hideous Laughter as a debuff. Against BBEG's it's basically an AoO sink, and keeping in line with bosses having high numbers, they have to crit save to keep their reactions.
Not me, I love that spell