The creator of the plugin "Death Messages Prime" has multiple "add-ons" you can add to make death messages prime better, one of them is DMPEnderCrystal which lets you make it so it shows the killer's name in the death message or whoever killed himself by blowing up a crystal, this is very useful for PVP servers where end crystals are the main weapon, the plugin is also supported on 1.16.
Here is the plugin's description:
This add-on is designed for DeathMessagesPrime, and adds kill and suicide messages for ender crystals under natural.EnderCrystalKill and natural.EnderCrystalSuicide, respectively.The config allows you to configure which player is considered the "killer"; the player who placed the end crystal (default) or the player that hit it, causing it to explode.Since version 1.2, tracking bed kills/deaths by player has also been supported.
Here are its supported versions:
1.9
1.10
1.11
1.12
1.13
1.14
1.15
1.16