Well that depends on rather you look to use small information you wrote before to write a whole concept or a plot twist using it, you can make it so no one knows he is a villain untill part 2 or rather make it new in part two which will work better if you are making a new mcs and protagonist, but there are some situations that need only to make it appear at part 2, which is the new protagonist is the child of the protagonist or one of the main characters, as it might seem off how he left the mc and rather get his children, but with a good plot twist this could work pretty well
hope that helped you out