Glorified Toasters Trophy

Notes:

- Deactivated Working Joes can be found standing in charging stations scattered throughout the first campaign but I don't know if they count towards this trophy.
- You can speed this trophy up by activating any Challenge card that increases the spawn rate of certain Synthetics (e.g. They'll Breed, You'll Die).

Combat Synthetics first appear during the mission "Giants in the Earth: Contact" but can also be found in the missions "Giants in the Earth: Evacuate" and "Only Way to be Sure: Breach". 1,000 Synthetics (AKA Synths) is a lot, especially since there aren't that many in the game so this trophy will take a while but the fastest way to kill a Synth is to headshot them with your best weapon.