200 kills with Final Heaven weaponskill on experience-yielding monsters of the plantoid family.
A good option would be to head to The Boyahda Tree and do page Page 4 (Korrigan and Elder Goobbue. Both mobs are plantoids, so you don't waste time killing mobs that don't count towards the trial. While you won't go /Thf the drops should still be decent for making gil off of wisteria lumber, boyahda moss and tree cuttings.
I found that @ lvl 99 I killed off the lower level Mandy or Goobbue too fast, and didn't even hit 100% TP before the mob was dead. So, I loaded page 3 from the FoV manual and would grab a Moss Eater to build TP once the Mandy was down to about 10-15% health. I could then simply Final Heaven the Mandy once I got enough TP. Do this enough times and you start completing pages. Prowess like Increased WS dmg and attack speed are very helpful for this trial.