From Main Lead to Villain?

Are there any tv serials where actors were roped to play the main leads anf then turned into villains and someone else became the lead. All I can think of are these two characters. Shreya in Tumhi Ho Bandhu Sakha Tumhi where she was the lead in all promos along with Neil and then suddenly she was turned into villain with the other brother and wife (played by Chandni) became the leads. Ragini in Swaragini, although she was a parallel lead but still a lead! Later the entire focus was on Swara and Ragini became a complete antagonist with very kaccha pakka redemption. We have seen lot of characters in negative shade turning into positive lead and that's quite a trope but has there been opposite?