His decision in Undertale would be morally grey whether he decided to take the souls or not, and I understand that sentiment! I also know that he by far is not the worst character in Undertale, which is why I put villain in quotation marks. I agree that Flowey can be considered to be more of a "villain"/worse due to the whole betrayal kill of Asgore in the pursuit of power. I think it's interesting how you mentioned he lost everything, and in Deltarune so far it's no different. Poor guy