See this method the name of plist could be slightly different( as you might be using older version of Malware bytes Anti - Malware for Mac but the location of plist will be in these folders .
For free version of Malwarebytes Anti -Malware for Mac .
Click on finder > Applications > right click on Malwarebytes Anti - Malware.app & move to trash , if it is in download folder , remove it from there also .
To enter in system library > click on Go > Go to folder & type /Library
Find folders : Launch Daemons > com.malwarebytes.Helpertool.plist
PrivilegedHelperTools > com.malwarebytes.Helper.Tools
To enter in user library > click on Go > Go to folder & type ~/Library
Find folders : Application support > Malwarebytes
Caches > com.malwarebytes.antimalware
com.malwarebytes.Malwarebytes-xpc- service
Preferences > com.malwarebytes.antimalware.plist
After update the new files that are found in system library .
LaunchAgents > com.malwarebytes.mbam.frontend.agent.plist
LaunchDaemons > com.malwarebytes.mbam.rtprotection.daemon.plist
>com.malwarebytes.mbam.settings.daemon.plist
PriviledgedHelperTools > a folder named com.malwarebytes.HelperTool
In user library .
Preferences > com.malwarebytes.mbam.frontend.agent.plist
Right click on these items inside the folders and move to trash .
Restart the computer & empty the trash .