Cave of Trials 4
Enemy Name: Omega popo
Enemy Hero: Omega Giant Popo X
Enemy Level: 4,000
Hero Stats: 1,200,000 HP / 55,000 Att / 3,000 Def
Aptitude: 0 / 0 / 0
Boss Spells: Special Attack
Popo Clone (Ex) - Earth, Pop 3, Cost 5.
BP Cost: 2,500 BP.
Exp Reward: 35,000 Exp.
Item Reward: Hero's Signature
Spam Centaur Lancers, as they have piercing attack, and, as he jumps, sending them into air, heal them, thus landing them safe and sound. Continue to stack lancers and victory will be assured!
You need 2000 attack on the lancers as well as a dragon egg for time. Elf Ranger+ do even better than lancers.
The fastest thing to farm this with is Fire Succubi with 1 Infinity Blade and 5 Demon Sword Laevatine. The succubi require somewhere around 6000 attack to be able to do it though so it isn't recommended until higher levels.
On Weight Watchers' most wanted list.