Back 4 Blood

Reason

While a major update added full offline support for the entire single-player campaign and its progression, the base trophy list contains two mandatory multiplayer/PvP trophies tied to the Swarm mode:

• “Squad Up” (Bronze): Requires you to form a party in Fort Hope (joining/inviting another player).
• “Swarm” (Bronze): Requires you to win a match in the PvP Swarm Mode, which strictly mandates matchmaking with and against real human players.

What Can Be Done Offline

Aside from those 2 online-only trophies, the remaining 54 base-game trophies can be completed 100% offline using AI bots in the Offline Campaign mode:

• Campaign Progression & Difficulty: Completing all campaign Acts on Recruit, Veteran, and Nightmare difficulties (“Act 1-4 Nightmare”) can be done completely offline. AI bots will assist with healing and infinite ammo perks, which can actually make certain high-difficulty acts easier to manage solo.
• Clean Sweep & Collectibles: Finding all secret golden skulls, killing 53,596 Ridden (“Good Riddance!”), and completing specific boss/level objectives can all be earned locally.

(Note: If you briefly go online to complete a single Swarm match win and party up with a friend, you can then disconnect and finish 100% of the remaining Platinum grind entirely offline).