In TestNG.xml how we can run a few cases only after when every other case has finished execution

I have a TestNG xml file that specifies which test cases to execute, but I can only run my test cases with "parallel=tests" strategy due to some framework level dependency. I have around 20-30 test tags, out of which one test tag needs to be run either before starting the execution of any other test tag OR after any other test tag. This means I don't want to execute any test cases from this test tag in parallel with any other test tag. How can I achieve the same without creating multiple test suites?