Access “Axis Invasion” from the “Play” option of the menu. You’ll search for a game and enter someone’s campaign mission and must succeed in killing that player.
You can use the phones around the map to reveal the location of the player (but it reveals you too). You can also make patrolling soldiers more vigilant to spot the player by clicking “RS”.
Upon winning, by killing Harry Hawker (the player), you’ll win the achievement.
I wrote a guide for Gamer Social Club:
https://gamersocialclub.ca/2025/01/27/sniper-elite-resistanc...