The Xbox One's backwards compatible list has just been bolstered by Left 4 Dead 2.
Yesterday the service received a few other titles such as Soul Calibur 2 HD, Halo Wars and The King of Fighters '98 Ultimate Match.
Fans have been clamouring for a Left 4 Dead 3 since Valve's sequel launched in 2009. Just last month diligent fans found files referencing a third Left 4 Dead title in Valve's Steam VR performance test. Of course, reports of such a game having been pouring in for ages, so don't get your hopes up just yet.