In your example, process 54 is the connection that you are using to execute the sp_who2 command. It is not doing anything unless you are actually running a command. And, as the error message from the KILL command says, you cannot kill the session you are using to run the KILL command.

I think you may be confused about how to read the output from the sp_who2 command. Chances are the CPUTTime and DiskIO value increase each time to run the command - this is because the sp_who2 uses CPU and disk resources to get the data required for the command to run.