So you can track that person that keeps changing their username
In the bot you can enable the log channel in this channel there will be messages if someone joins or leaves your server
Configurable logs, every action you'll know it even channel's permissions overwrites.
Mirai allows you to define an event channel where selected events are recorded. This allows you to have an easily visible log of moderation actions with their reasons. Username and nickname changes can also be logged.
Wick will log anything security related in a channel of your choosing. (Anything Wick does will be logged)
Includes extensive server logging that can be configured to appear in a specific channel
Fully configurable logging system.
It offers a granular logging system for messages, member updates, server updates, moderation actions and automod actions. The dashboard also has weblogs
Logs many servers into a channel named #bump
Kashima also have logging like role changes, message edits / deletes (although she might not do well in message edits / deletes due to cache), welcome messages, member changes and things you would want from a logging system.