IIRC there is some option under tools or options... something like "remove deleted games" or "pack database" something like that. Maybe the option is easier to find if you right click?
Chessbase - How-to question

In the main window, click on the database, find mainentance in the menu ribbon above, and chose remove deleted games.

I misread your question. I don't know the answer. I had the same problem in one of my databases. I restored the database from a back-up copy and deleted the database with the mass of games mark for deletion.
As far as I know this can only be done by manually selecting the games. If you have a backup of the database or are able to reinstall it that may make it easier.

Ziryab and All, thanks for the comments. Glad to see that other were having the same problem. To restore from backup is an option, sure.
But...
Tatzelwurm, if that is as you write that is amazing. I'm gonna check that out and report.
Later,

Tatzelwurm,
you are my hero now!! That filtering worked. It gives a list of all deleted/strikethrough games. Then mark them all, press delete again, and they revert back to normal/non-strikethrough.
Excellent, well-hidden feature of CB12... this has been bugging me for a long time. Now it's solved.
Thanks again!
I have ChessBase 12.
I "deleted" a bunch of (double) games in a database. That is the games are now in "strikesthrough" but not yet actually purged from the database.
Is there any way to GLOBALLY "undelete" these games again? I am trying to filter for them but I cannot create a list of just those "deleted" games.
I know I can select them one-by-one and press Delete button again and they will go back to normal (non-strikethrough). But that's tedious/impossible when there are many in a big database...
Many thanks for any help.