When Regina pulled Snows হৃদয় out she sad it had darkness in it, meaning Snow will one দিন be bad. Is that actually going to happen? Will Snow turn bad?

Snow made a mistake. But she didn't embrace the darkness, as long as Snow does the right thing from now on I don't think Snow will become bad.

In the show, it isn't as simple as a character being good অথবা bad, a hero অথবা a villain (one of the many things I like about it). Having a spot of darkness in her হৃদয় is a symbol of how Snow has done something wrong অথবা villainous. It doesn't automatically mean that she's going to become a villain. It doesn't indicate anything of a character's future.