Immunity

I still think that it's a stupid decision to make certain zombies completely immune to certain weapon upgrades with zero damage. I get it, they are immune to damage they mutated in, but there is never only like electricity damage when attacking with bat with electricity upgrade, there is always the hit damage as well.

This only makes me to use certain weapon upgrades less and use the physical upgrades way more than anything else because it's superior and you can use it against everyone. I only use acid or electricity weapons when I find some already like that.