It's been a long time coming, but a patch has finally been released for https://www.trueachievements.com/Left-4-Dead-xbox-360.htm that fixes the Sacrifizzle achievement!
Not only that, but Valve have stated that the new patch will recover the progress lost towards achievements when "The Sacrifice" DLC launched. If you were one of the unlucky folk who lost your progress towards achievements like Zombie Genocidest and What Are You Trying To Prove? should find all that progress now restored, and added to any new progress you've made since then. This may not be the case for everyone or for every achievement, but Valve have stated that "the majority of players should see their progress restored."
This patch also contains all the game tweaks and fixes that Valve patched into the PC version back in October, listed below:
• In Versus mode Tanks will spawn in stasis until a human player takes over. Tanks in stasis are invisible and invulnerable, and won't move or attack.Rejoice! The full 1,500G in https://www.trueachievements.com/Left-4-Dead-xbox-360.htm is now obtainable!
• Tank speed is no longer reduced when on fire.
• Allow players on the Infected team to manually spawn during finales.
• Added a vote option to toggle All-Talk.
• Special Infected that causes a Survivor to stumble into a "ledge hang" situation will receive 50 points.
• Bullets that first pass through an infected character before striking a Survivor are now ignored as friendly fire.
• In Versus mode car alarms will now trigger anytime a Special Infected pulls or stumbles a Survivor into an alarm car.
• Survivor Bots no longer try to melee exploding barrels out of their way.
We've got the full list of Left 4 Dead achievements - check the list for guides to unlocking them.