Please make sure that you did the following:
- deleted all CLM servers from each domain
- installed DB on all domains
If this is the case, login to the global domain,, make sure there are no other admin sessions at this time, install DB and try removing MLM object once again. Check $MDSDIR/logs/cpm.elg for errors. There should be some more details about removing MLM object.
Install DB again and run cpstop/cpstart on your MDMS, or reboot it.
If after all things above, you still have MLM showing up, it is a good idea to open a TAC case.