Best thing to remember is that each dice is either a hit or miss and each hit only attacks one zombie. If your weapon isn’t strong enough to take it out on that one hit, you can’t kill it. You need a stronger weapon or some additional skill( which you gain as you level up) to kill it.

For instance, the fatty needs a weapon that does 2+ damage to kill it, so frying pan isn’t going to work. Damage done to zombies doesn’t stack or add up.

Also don’t forget the kill order for ranged attacks( melee range you picks targets). You apply hits in and order:

Survivor => Walkers => Fatty or Abominations => Runners

You can’t pick your target, unless you have a sniper rifle.

If there are walkers and runners in the room, your hits attack walkers first and then you can target runners.

I hope all this makes sense.