Well, anti-oxidants are helpful, but for different reasons. Typically, each anti-o affects only certain areas of the body, not necessarily targeting muscle tissue or whatever the aim is. For instance, NAC is helpful to a number of tissues that receive oxidative damage, including the liver and testes. Vitamin E complexes help a number as well. But not all are equal.
I cant speak of multi-vitamins though and I suspect many are bunk or not properly dosed. Since the supplement industry is not regulated at all, I try and avoid supplements with lots of different mixtures of vitamins, minerals & amino acids. It makes it nearly impossible to tell if the stuff if working & since there is no repercussion to companies that are lying about their advertised prodcuts, I dont take the chance with them. When you buy products that are sole compounds or only a few, it is easier to assess its effectiveness.
This is why I've always trusted the purchase of pre-workouts & steroidal compounds really. It's hard to lie about your product being legit or not when it comes to those two. At least there you know what you're getting and you only get fooled once.