Alright, I shall give reasons why L4D2 is not needed:-New campaigns could have been added. L4D has DLC for a reason.-Survivor packs for DLC, usable only on certain maps.-Other stuff that can be solved with DLC.Seriously, not needed. At all.
Source filmmaker
Be reminded that the movies are usually made with the Source filmmaker, with fancy stuff added.
Tank looks weirdish lol
The Charger pile drives you into to ground repeatably til you die, how cool is that.