Go Big or Go Home

Win a match using only capital ships.

The non-capitals that you start the match with don't count and are fine - you can use those. Regular trading vessels are ok too.

But any other ships acquired through the match may/will invalidate this achievement, so...

• don't research the items in the civilian tree that grant trade escorts
• as TEC Primacy, don't build the Pirate Mercenary Base (so you can't get Privateer in the same match)
• don't use any garrisons
• don't use the Advent's Rapture ship to capture other ships
• don't use any raiders

It can help to sell off your Light Factory early on to avoid accidentally building something smaller and invalidating this achievement for the match (which is why it is soft-missable).

This is the opposite of Fear of Icebergs and both cannot be unlocked in the same match.