Essentials

Essentials is a plugin that provides over 160 commands. The plugin has been in development since at least 2011.

The original Essentials plugin was discontinued in 2015, however, a fork called EssentialsX is still maintained to this day and is what is used on the Kaboom server.

/gc

gc is a command provided by Essentials that displays server metrics such as RAM usage, loaded chunks, block entity count and TPS. Unfortunately, their implementation uses an older part of the Bukkit API which unnecessarily creates a clone of all block entities, leading to severe lag spikes when the command is invoked with lots of block entities. Fortunately, this is patched in PaperMixins.