What are the anomaly tiers and how do they work?

Anomalies in Animal Hospital Anomaly are ranked by tier from S (most dangerous) to C (least dangerous). S-Tier anomalies like The Watcher and The Morgue Keeper are extremely deadly and require careful strategy to avoid. A-Tier threats like the Distorted Patient and Nightmare Hound are dangerous but manageable with the right approach. B-Tier anomalies like The Warden or Contamination present moderate challenges. C-Tier threats like Blood Stain or Infestation are more nuisance than lethal but can still cause problems if ignored. Always check an anomaly's tier before formulating your survival strategy.