Usage: UMODE k
Usage: MODE <nick> +|-k

k - KillMode:
Will show you all the kill messages occurring on your server and the network. On a big network this will often be more information than you want to deal with, although you could set up a bot to log it in case you wanted to be able to check for any problems later. On smaller networks this can sometimes help give you a better feel for what is going on.

Privilege: Operators

/mode Dan +k
/umode +k