This is no longer unobtainable thanks to the following workaround. Credit to Der_Schwabbler from the Ubisoft community Discord for sharing this.
From the main menu: Map Editor > Create New Map / Assault > Start Map Editor
Set a Spawn Point (L1 > Add Gameplay Objects > Player Spawn Point)
Add an Enemy (L1 > Add AI > Enemy Wave 1)
Press Start/Options > Save (A warning message will say the map has not passed validation tests. This is fine, select Yes)
Save the map and give it a name
Exit to main menu
Go to Map Editor > All My Maps > Select your map > Play
Kill the enemy or die - the trophy will unlock after the game finishes