Versions

• Minecraft: 1.12.2.

• Forge: 2854.

• Vampirism: 1.6.2.

• ModPack: Yes. Mods listed in the report.

Crashes due to something related to Hunter Villagers.

crash-2020-12-19_16.10.15-server.txt

Join a world.

N/A

This is caused by the mod "VampirismFix" (I assume it is this one on Curse https://www.curseforge.com/minecraft/mc-mods/vampirism-spawn-remover).
It seems to be outdated and does not work with the newer 1.12 versions of Vampirism. You can try to contact its author

Not really sure if that mod is good for anything anyway. I don't believe it greatly reduces lag and if it removes the hunter spawns it more or less breaks Vampirism as you cannot progress.