It is possible to reach Cactuar Island with Balamb Garden because a small portion of the Kashkabald Desert is part of Cactuar Island, which itself is currently inaccessible (one cannot fight Jumbo Cactuar like this). To reach this area of the world map one must pilot Balamb Garden to a small gap in the mountain range surrounding the south of the desert and proceed on foot.
Cactuar is a fast enemy, and is likely to escape before anyone can attack if the party has low speed stats. The 1000 Needles attack ignores evade and status effects such as Protect and Defend, and will inflict 1,000 HP every time. Cactuars grant 20 AP when killed, making them good prey for learning new GF abilities.
Cactuars are weak against Water, so Water spells or summoningLeviathan work well. Although Cactuars have massive evasion, Squall's 255% accuracy guarantees him a hit. Selphie is the only other character who can attain a natural 255% accuracy with her Strange Visionultimate weapon. The other characters can boost their accuracy with junctions. Junctioning Water spells to attack makes them deal double damage, but Cactuars already have low HP.
The Initiative ability lets the user start the battle with a full ATB gauge. One strategic setup is junctioning Initiative to Squall, Irvine, or Quistis and have them use Limit Breaks that damage all enemies, i.e. Fated Circle, Scatter Shot, or Ultra Waves.