Fortnite.
Embedded on the live-service QA team for one of the largest games on earth. I pressure-tested the player experience layer, which meant hero loadouts, inventory, mission select and progression feedback, then translated the friction I saw into something the design team could actually act on.
This was Save the World, before anyone knew the name. Three months after my engagement ended Epic shipped Battle Royale as a free add-on. It hit 45 million players in 90 days, running on the systems I had been testing.