Stellaris

This achievement can be combined with Into the Unknown.

Start a new game with the Overlord DLC enabled and choose the Slingshot to the Stars origin story for your empire. The galaxy can be any size (smaller is easier), but choose no AI and one Fallen Empire.

Only expand a minimal amount and focus primarily on repairing the Quantum Catapult. Once it is operational, send 10 Science Ships through it (for Into the Unknown) and then build 50 corvettes (it is cheaper if you build them with no weapons or defenses).

While you are building the corvettes, use your Science Ships to find the Fallen Empire if you haven't already. When your corvettes are ready, split the fleet repeatedly until they you have 50 fleets with 1 corvette each, and move them all to the system with the Quantum Catapult. Place a claim on the capital system of the FE and declare war. Exit the game and make a backup of your save file, and then start the game up again. Select all 50 single-corvette fleets, click on the quantum catapult option in the menu bar on the top fleet, and send the corvettes through the Quantum Catapult targeting the home system of the FE. If none of them land in the home system, exit, copy your backup save file to the savegame directory, and try again.

Yeet the Fleet will unlock when one lands in the capital system of the FE.

if you make the quantum catapult close enough to a neighbouring empire and level it up the stage I did it on was stage 3 so 25000 alloys should be cheaper with a closer pulsar star. make enough armies hold v on the armies so they are individual ships and get them to the pulsar and hit the jump button and wait the time with luck you will get a ship to jump to the right system (if you are like me 138 armies only 2 made it and over 58 mia for 4 months)