Deleting a suspicious malware (imklaunchagent) in Mac
You can't (see † below) remove that file because MacOS doesn't let you (or anyone) alter the contents of /System. Only Apple can write to that location. 

MacOS does that to ensure the integrity of the OS. In other words, if it's in /System, it's part of the OS.

† By 'can't', I mean in the normal running of your computer, unless you yourself follow a particular procedure which no active software can perform by itself as a means of corrupting your system.