There are several places that allow accumulation of vasy
CP. Although many are only accessible (or practical) at or after the endgame, this is also the point at which they become particularly useful. One notable spot is the penultimate configuration of the Tesseracts in
Orphan's Cradle, where a moderately powerful party can defeat the lone
Wladislaus in about two minutes (using a slightly risky Evened Odds → Relentless Assault strategy) for 32,000 CP, and it can be respawned quickly by returning to the lower
Save Station. This is a good spot, but one which can never be revisited after the Tesseracts undergoes the final reconfiguration to access the final bosses.
Another popular spot is in the
Archylte Steppe near the
Mah'habara Subterra entrance with the fighting
Behemoth King and
Megistotherian pairing; the party will always get a
preemptive strike, and both enemies will be at half HP. One way to kill them is to
stagger the Behemoth King and use the
Commando's Launch ability to prevent it from replenishing its HP, then killing the Megistotherian. With a strong party the battle will only take approximately 7-14 seconds for 6,600 CP, or 13,200 CP with a
Growth Egg.
One popular training method, especially for lower levels, requires the player to repeat Mission 24 in
Taejin's Tower with each battle yielding 6,000 CP (12,000 with a Growth Egg). The reward for completing the mission is a
Moonblossom Seed that can be sold for 6,000 gil, and it takes only a few seconds to walk from the
Cie'th Stone to the Mark, making Mission 24 a good method of getting quick CP with some gil on the side.
In the optional area of the Mah'habara Subterra mines (access granted by riding
Atomos back from
Sulyya Springs), one will come across an area with six
Cryohedrons. They can easily be killed in a matter of seconds for 7,140 CP each time. The bombs will respawn when the player backtracks a little.
A formation of five
Pulsework Gladiators can be encountered on Fifth Tier of Taejin's Tower. As each one grants 1,600 CP for being destroyed, defeating them will grant 8,000 CP per battle.
As an exception of this endgame rule, a relatively early grinding spot is within the Estheim Residence during Chapter 7 where the party is ambushed by
PSICOM troops. Two enemy parties appear in the small map, and so as long as the player eliminates them both and moves to the back of the map, they will keep respawning. This point is specially rewarding in gil as the PSICOM troops here drop
Incentive Chips, which can be sold by 2,500 gil in the nearby Save Station, and often drop more than one per battle. While the CP is not as rewarding, the potential accumulate of CP one can acquire while grinding for gil can be large as the enemies are not hard to defeat and yield around 160 CP per battle. And while perhaps not useful for the current party they can be useful for
Vanille and
Sazh who are used next with an expanded
Crystarium.
The Adamantoise in
Eden is right next to a Save Station allowing for a quicker restart. It is possible to have Vanille spam
Death on an Adamantortoise, which can yield 40,000 CP (80,000 with Growth Egg).
With some patience, ten minute runs through the
Faultwarrens can yield around 75,000 CP (150,000 with Growth Egg). This includes all of the non-marked enemies along the way. Primeval Crossroads → A Dance of Shadow → Via Stellarum → Salamandrine Path →
Titan's Trials (Mission 47,
Raktavija). Of note are the
Cactuars on the Salamandrine Path, which give around 7,500/15,000 CP each if defeated. There are eight of them, but they run from battle if given the chance.
Attacus (Mission 51) gives 75,000/150,000 CP when defeated, although that battle typically lasts at least 15 minutes. Everything considered, an hour in the Faultwarrens can yield almost a million CP. A caveat, though—it's best for the player to be farther along the Crystarium to attempt this, as the fights can be tough.