Partially assembled can mean a lot of things so I'm curious as to what people have had to do with various brands/makes/models. (Discounting the usual seat/handlebars dance to get it fitted to you as the individual)
I'll start off with my Addmotor Motan M-560 P7 where the Basic assembly consisted of;
Mounting the front tire in the forks
Mounting the handlebars on the stem
Attaching the pedals
Attaching the fenders and front light
Inflate the tires
Charge and mount the battery
Additionally
The front brake was horribly misaligned (rear was perfect)
Derailleurs needed some fine-tuning (they were super fiddly to work with for some reason)
Handgrips kept moving around, had to remove and treat w/soapy water. After drying they stayed properly in place.
Snug multiple bolts up to acceptable torque (mostly on the headset and handlebar controls)
NOTE: Addmotor included a fairly nice and complete little toolset with the bike that took care of all the assembly/adjustment needs though I found I preferred my longer hex-wrench to torque up the seat.