The Crystalline Entity...a 'fleet action'? A fleet slaughter! The Crystalline Entity is an abused, defenseless creature who is routinely killed by both Starfleet and Klingon captains, which is APPROVED as well! Such is their cruelty that a few captains keep a piece of the Entity as a TROPHY of their so-called 'victory'.
A few have even recorded their 'battle' against the entity as well: