Just number the scripts, like 01-firstscript.sh, 99-lastscript.sh, if it is showing in last in ls -l, you're done.
It is all about the file name. If the files are not supposed to be numbered (installed by distribution), just change the name of your own scripts to have something like a zzz-001.sh, zzz-002.sh, zzz-003.sh etc....