The game unfroze, but it was a slideshow. The boss teleported across the screen. Sarah’s character was running in place against a wall. The latency was unbearable.
"What? What does that mean?"
The primary reason is that your router or firewall is blocking the inbound connection required for a direct "Green" link.
The Windows Firewall or a third-party security suite might be blocking the Hamachi Client Tunneling Engine (hamachi-2.exe) from receiving data.
The fallback. Data is "relayed" through a middleman server, significantly slowing down the connection.