Theory::
Emma’s visions are only the “possible” future. She is seeing the outcome of what will happen if she uses the shears and severs herself from her “Savior Emma side”
This is a parallel to Regina/Evil Queen. What happens is that by severing themselves, they dont get rid of any sides, they only bring their inner fights to the outside world.
What Emma sees in her visions are Dark Emma killing Savior Emma (like we have sort of already theorised) It was said in the episode, that the Savior always dies… Hmmm so maybe thats what always will happen if you use the shears.
This is therefor allso what happened to Aladin. The dead corpse in the crypt (which also had the scarab) was dead “Savior Aladin” and the Aladin who is still walking around, is Dark/bad/some-type-of-evil Aladin.