Add the entire Resident Evil 6 installation folder to your antivirus to prevent future blocks.
Corrupted Steam API files are the most common cause. Resident evil 6 black box error failed to initialize steam
A missing or quarantined steam_api.dll file is a primary cause for this initialization error. How To Fix Steam Initialization Failed Add the entire Resident Evil 6 installation folder
Missing .dll files in the Steam\steamapps folder. Resident evil 6 black box error failed to initialize steam