I've been playing around with melee theorycrafting lately. In general, the highest DPR build that's actually practical seems to be a fighter who uses Certain Strike and Desperate Finisher to make lots of attacks with a forceful weapon. However, I am pretty sure the highest DPR available in the Pathfinder Playtest is via a 20th-level monk who's flanking.
Perfected Form opens interesting possibilities. While it's normally only possible to hit level-appropriate enemies on a 10 when you're not suffering from the MAP, the fighter's Agile Grace feat and other conditional or circumstance modifiers can combine to make guaranteed hits on multiple attacks viable in the right situation. This can yield Kenshiro-level fun. Here's a sample build.
The Build
Necessary Feats: Wolf Stance, Ki Strike, Fighter Dedication, Basic Maneuvers (Double Slice), Stance Savant, Diamond Fists, Advanced Maneuvers (agile grace)
Important Assumptions: Diamond Mind's circumstance bonus for already-forceful weapons stacks with forceful's (inconsistent with RAW, obviously RAI); Double Slice can be used with unarmed attacks (debatable for both RAW and RAI).
Assume a hasted 20th level monk optimized for damage: 24 Str, +5 handwraps of mighty fists with keen and 2d6 energy damage worth of property runes. This monk is attacking with wolf jaw, a 1d8 agile piercing unarmed attack that gets forceful if they're flanking. Assuming they are, that's 6d8+2d6+7 damage on the first attack, with a +9 circumstance bonus to damage on their second and a +17 on their third, for averages of 41, 50, and 58 respectively.
Unassisted, they hit AC 44 on a 10 or better with their best attack, down to 14/18 from the MAP on agile unarmed attacks. Agile Grace takes this to 13/16. But let's assume the monk is indeed flanking, taking this down to 11/14, and--finally--that they're willing to blow through their SP for a ki strike nova, the +1 conditional bonus takes you to 10/13: enough to guarantee a hit on their second attack! They thus do the following:
--) Strike (extra action from quick): 49.2 (1.3 x 41) expected damage.
--) Double Slice (attacking twice at -3): 118.8 (1.15 x 50 + 1.15 x 58) expected damage.
--) Flurry of Blows (attacking twice at -6): 61 (0.5 x 58 + 0.5 x 58, plus 0.25 x 12 from the chance at extra damage from the monk's Fierce Flurry) expected damage.
In total, that's 229 DPR: more than a fighter can do with Desperate Finisher, and unlike with Desperate Finisher, it doesn't eat up your reaction.
However, it's possible to do better. An 8th-level Heroism replaces your one-round ki strike nova with a nice steady 10-minute +3 conditional bonus, bringing you just one measly point away from guaranteed hits on ALL your attacks. And there are lots of ways to make up that deficit: one of your allies can assist you or make your target sluggish. If you can do that, the same sequence reaches an eye-watering 325.85 DPR. Since that's around the maximum hit points that 20th-level enemies have, and every attack is an automatic hit, this will virtually guarantee a kill.
(For even more damage, you could take Ranger Dedication, Basic Hunter's Trick (Twin Takedown), and Targeted Hunter to get six hits after the first round. However, this is probably useless in practice: no target with an AC low enough for this tactic to work will have enough HP to survive more than one round of it.)
Note that one reason why this is interesting, apart seeing how high the numbers can get, is that it's yet another indicator of how tight PF2's design assumes the math to be.
On its own, Perfected Form is neat-but-not-incredible capstone. But if you can push it past the narrow boundaries of its expected functionality, it blows the roof right open, damage-wise.
I'm still unsure if Double Slice works with Natural Attacks. Paizo should really state outright if Natural Attacks/fists can count as "weapons".
I'm still unsure if Double Slice works with Natural Attacks. Paizo should really state outright if Natural Attacks/fists can count as "weapons".
I'd also add that if Double Slice DOES only work with manufactured weapons, you can still exploit Perfected Form with Flurry of Blows -> Strike -> Ghost Strike, usually yielding three guaranteed hits against equal-level opponents. The Void property rune can also work well for this purpose.