Plastic pry tool and or fish line to cut the foam adhesive tape. A lot of times, a slow even pressure on the corner of the emblem will cause it to come off. I recall that some emblems have posts that fit alignment holes in the sheet metal. So be careful.
Some emblems. I wish I knew about mine! Maybe I can start at it and it'll become obvious along the way?
Which emblems? The side Hybrid emblems are double sided tape as well as the rear Prius Prime emblems. The front emblem is more fastened. But the sides do look better de-emblemed (see my avatar).
Here's a pic from the local Craigslist that shows the front section: Toyota Prius prime - auto parts - by owner - vehicle automotive sale The front emblem probably attaches the same way. Why debadge the front?