How to get Gilgamesh to use his Limit Burst?

i think if he has surplus ap then he will use it. maybe try bells?

So he's broken? I need to turn off his best ability to use his Burst??

The AI prioritizes the most suitable damaging skill with the most efficient use of AP. Kotetsu beats it in both criteria, so Flash is very unlikely to get used while you have remaining uses of Kotetsu.

Flash was designed as an Arena tide-turner for a magic-support-built Gilgamesh (Haste+Quicken on you, Slow on the enemy). And yes, with Kotetsu turned off.