Essential's /nick - how to know who he is?

Let's say 50 people online.
Someone change his nick with /nick to SuperHater and start saying the admins are shit.
How can we know is this dude dud1, dude2, dude3... or dude50 that wrote /nick SuperHater?
What is the easiest way to detect who who is when people can change theyr nick with essential's /nick

/bump

EDIT by Moderator: merged posts, please use the edit button instead of double posting.

 

You can either use /whois SuperHater, or /realname SuperHater. /whois should only be given to mods/admins, as it shows the player's IP, among other information. /realname is pretty innocuous, just spits out their pre-/nick name.

 

Yep
Just do

Code:

/whois <name>

or

Code:

/realname <name>

 

@c0mp , @Chillax_Team oh thank you guys!

I thought that for /whois I need to know the real name, not the fake one, and I didn't know about this /realname - will give it to users.

 

Anyone have an idea why /realname has never worked for me? Does anyone know of a plugin that causes this to stop working?

 

You kick all your players one by one and you notice the name everytime you kick someone.