When a player damages another player, both into "combat mode". If you disconnect while in combat mode, you die!
With lightning effects and a special death message!
"Cooldown" time (time you need to wait before disconnecting after giving/taking pvp damage) is changeable in the in-game mod config menu. There are some other options in there as well, for removing the lightning effect, setting the death message, etc.
Yes, you can use it in your modpack if you want (MIT license).
A list of my curseforge mods can be found here
