This is dependant upon the IRCd that the server uses and also whether the network uses Services that may aid IRC Operators - for example, OperServ.

Really the only way to find this information is asking the network/server administrator (i.e. your friend) and asking them to tell you what's available. There are often quite a few different levels of IRCop and what is available to one type of oper may not be available to another.

Two commands which are available to all opers are the /kill and /kline commands, which disconnect a user or ban a user from the server respectively.

You could also search Google for information and look for help documents related to the IRCd that you use.