CombatLogX is a pvp-based plugin that punishes players for logging out during combat.
There are many configuration options, such as punishment type and commands.
CombatLogX also has a lot of expansions that are used to add extra features and keep the main plugin lightweight.

Plugin Link:

https://www.spigotmc.org/resources/combatlogx.31689/

Donate:

http://bit.ly/SirBlobmanDonate