SQL Server 2014 SP2 CU10 Patch uninstall stuck at DowntimeTimingConfigAction
So I figured this out, Posting an answer to help out anyone else who is stuck.

When SQL updates a set of scripts is run on the system databases to make sure everything is set up right for the new version of SQL. When you uninstall an update it has to do the same thing but backwards.

In this case the backward scripts for 2014 SP2 CU10 back to base 2014 SP2 do not stop SQL correctly. So you just need to make sure to stop the SQL service first before running the uninstaller.

So to do this downgrade follow these steps for best results:

1. Restart the server, (make sure there are no other windows updates pending)
2. Stop the SQL Server Services
3. Uninstall the SQL Update
4. Start the SQL Server Services (start the 2ndary services first like Agent and SSRS first)
5. SQL will then run the downgrade scripts and will be happy after 5-10 minutes.
6. Restart the server again for good measure.


If your stuck at the place I was the way to get out of it is:

1. Open SQL server configuration manager
2. Open the proprieties of the SQL Server Service
3. Go to the Startup Parameters, add "-902" startup flag
4. Restart the server
5. Wait for the server and SQL to come fully back up
6. Remove the startup flag
7. Restart the SQL Server Service


Then Follow the first set of steps to fully remove the update.