I received a VAC Ban after using this Trainer 300+ days ago, wish I had read the instructions first. It works for Single Player, Multiplayer does not work at all, but still will receive a VAC Ban, for those who use Trainers, do not make my mistake and play Left 4 Dead 2 in Online Mode of Steam XD
All in all. Love the work from MrAntiFun
P.S. There's a Workshop item that allows you to be Invincible and allows it to be in Left 4 Dead 2 online if you are worried about being VAC Banned.