I use a chisel + hammer, with the chisel flat against the face of the blade (not across the face if i can help it, but angling to the side to make the least scratches). I tap the chisel to get under the handle. Once it is completely under the handle and if it isn't snapped off yet, I carefully twist the chisel (the pivot point furthest away from the face of the blade) and the handle pops off. Sometimes it comes off easily (Pro Pro Tigress) and sometimes difficult and it doesn't even remove the entire handle (yinhe t10 / xvt carbon balsa) in which case it needs to be files flat, smooth and even.
If I was concerned with damage from the handle being removed (it has happened once to me), I would use something like a Shinto rasp to file it down flat, but this will require more time and a lot of skill to get it flat / event and stop at the correct time.