"Best time 19s."
Proof?

"My best time is 32 seconds for all 5 rounds"
Today rich 28 sec for 5 rounds.

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after you beat the game go to chapter 17 and proceed to the battle sim. put magnify+fire/first strike on cloud and do two-person team vs high flyers. wipe out the first round then give up and rechallenge. repeat over and over. costs 400gil each time but gets you 48 ap in about 10 seconds.

Best time 19s.

Correction. 30 to 33 matches per hour... 5000AP per hour per materia. (i set all long AP materia like HP/MP UP or revive)

Each match gives total of 165 AP (post endgame), i average can get 30 to 33 matches (remember to set all short to max AP together and long to get AP together, this will lessen your time to switch MAX materia to new materia. You can use triangle to rechallenge for faster...

The last round sometimes need luck... I tried blizzaga and all 3 monster stay together (blizzaga second explosion is AOE even no magnify) then i cast second blizzaga (my ATB reached 1 bar). My best time is 32 seconds for all 5 rounds, average 1 min 5 seconds, 1m 30s top

Pt4. Final round. When start round, cloud dash front once and immediately use blizzaga on any monster, once he cast it, attack on the monster that he shot. Keep use blizzaga and sometimes the monster low hp, use barret overcharge and when his atb full use his focus shot...

Pt3. Round 4. This is abit complicated but after pratice, it is easy. Firaga all on the enemies infront then switch to barret and lock target, switch to sentry on left (he can stun, so kill him first) use overcharge (triangle) and normal shoot on sentry on right until two ATB full, then focus shot.

Pt2. Round 1 and 2, once enter the battle, use shortcut (R1+O for me) to firaga all enemies, mostly 1 shot kill all. If not, switch to barret and use overcharge ASAP
Round 3 same as round previous but MUST switch barret and overcharge the frog guy... (Lock target and shot)
Round 4... Tbc

Fastest AP farm i found. At chapter 14. Go to corneo colloseum. Equip most slotted weapon plus one connected slot (weapon or armor) spend 4 slot for fire+magnify, ice, first strike. Set R1+O firaga all, R1+X blizzaga on cloud, R1+(any) focus shot. Once you enter the match (3vs shinra warriors).