They do not hurt. They do not stagger. They do not tire. They do not fear. They do not think.
All they do is hunger. They will never stop. And as long as they know you exist, they will keep coming. And you will never kill them all, not with any weapon, especially not your muscles.
Run, run to a place the zombies cannot follow.
Are you kidding? They stagger constantly. It's their shtick. And it's pretty simple to kill them all. Wait about seventeen months.
1 gram of fat contains 9 Calories of usable energy (protein has less). Assuming a first order Taylor zombie approximation, for a 200 pound zombie made entirely of fat, you get about three and a half million joules of energy available to your zombie.
Walking burns 4.6 Calories/minute. So, overestimating the energy they have to work with (zombies don't actually process or eat anything - the just kill it and lose interest), the theoretical blubber zombies I proposed are going to last for about 529 days at maximum.
Now, given that they'll end up damaging themselves, can't stop decomposition, lurch in an extremely energy-inefficient manner, won't have nearly as much energy to begin with... zombies just don't seem like a feasible long-term threat, as long as they no longer can continue making more. Given how slooooooow they are, unless they're in mobs they won't be able to hunt people down - but if they're in mobs, then they're easier to spot from far away, they won't split up because they all have the same incredibly stupid instincts/programming, and they're less of a threat than a single zombie hidden in the woods. The mob'd probably get eaten by crows or a hyena or a dingo dog or something.
Honestly? Zombies are either a perpetual renewable free energy source, or easy food for the buzzards. One way or another, they're not a credible threat, although they may be a natural resource. And besides, if Septerra Core taught me one thing, it's that throwing bread at zombies is the most effective means of killing them.
Vampires, now... especially vampire dolphins. Totally different matter. Native echolocation + streamlining + massive undersea areas to congregate... don't want to have to deal with them. With fangs, vampire dolphins might be able to compensate for their inherent lack of thumbs, which
nobody wants.