If the curse was created for Rumplestiltskin, either by himself or someone else, I don’t see how he could have enacted it. It requires the heart of the thing you love most. The only time I can assume Rumple would have wanted to use it would have been after he lost Bae (however that happened) or after he lost Belle. In either case he wouldn’t have had the heart. He thought Belle was dead, and I cannot imagine him killing Bae to help him forget that he lost Bae.
And if he just wanted to forget his own pain, wouldn’t there be some other way to make that happen? Using the curse for that end would make him a sort of suicide-bomber amnesia-curser. It’s not that I am saying he is above that. I don’t know that Rumple loses a lot of sleep worrying about other people’s pain. But this curse is intended to make other people suffer. It is only going to be used by someone who seriously hates other people and wants to inflict pain as revenge.
If Adam and Eddie follow the pattern of Lost, then each season gets a new villain who makes last season’s villain look “positively moral.” Can’t wait to see what happens!