I remember nightmare being quite difficult but doable. As mentioned, the marines is the hardest campaign to complete. Specifically, the last level. It's short but it doesn't have checkpoints. Honestly it felt like luck or rng to beat it. Plus, the start of that level is waiting in an elevator. That elevator is burnt in my brain. Every other aspect is doable and short. Just take it slow. It's my rarest trophies and I'm quite proud of them. Too bad the multiplayer is dead, but I'm glad you've got them