PSA: Optimizing apps 1 of 1 got you down?

I can't see how I have an offending app. I deleted every single app that can be deleted, and I get the optimizing error when booting in safe mode. But factory reset has cured a few different problems with this tablet in the past, so I think it will this time, too.
 
Hard to say. It could be a combination of the older OS version trying to reconcile with the more recent app versions that are available for the preinstalled apps.