Asriel Dreemurr is the most tragically screwed over character in UNDERTALE. I don't think anyone can deny that.

However, recent reddit posts have found that, if Toby follows his own logic, it is impossible for Asriel to turn back into Flowey, mainly due to the link between Chara and Frisk's souls. 

(Which could only have been forged through Asriel's, as humans cannot link their souls to other humans.)

So, sign this petition, or else you are a horrible person.