Hi OwlfromAthens,
Both kextload and killall are built-in commands for macOS, preinstalled by Apple. kextload is an old command that is used to load third-party kernel extensions into the macOS kernel, and should be mostly avoided for security reasons. killall is used to terminate running processes that match a specified name. The reason why they are showing up in the Login Items is because a third-party developer is using them as part of their application(s) or script(s).
To see which developer is using these tools in this way, open a Finder window. Then, at the top of the screen, choose Go -> Go to Folder, and paste in one of the three paths provided below:
~/Library/LaunchAgents
/Library/LaunchAgents
/Library/LaunchDaemons
Several files should appear in those locations. Do not delete any of them. Instead, open each one in TextEdit and check if the file contains either "kextload" or "killall" in it. If it does, note the name of that file; it will help you track down which app is using those commands in that manner. Usually the file is named after the app's developer, or after the app itself.