Using Ochettes Provoke Beasts ability you can summon a single use monster up to 6 times here's how

Step 1, Max Boost
Step 2, Open Provoke Beasts menu by selecting the skill
Step 3, Activate Latent Power while still in Provoke Beasts menu
Step 4, Close Latent Power Menu and Open Standard Summon Beast Menu
Step 5, Click on Scourge of the Sea 6 times
Step 6, Watch as you break every shield on the final boss in a single turn