"What if...?" Episode 4 Explaied , Evil Doctor Strange distroyes the universe

 What If... Doctor Strange Lost His Heart And Not His Hands : 

We've watched one moment or one choice can ripple across the space and time and time and making a whole new different world. In this world Strange didn't lose his hand this time he lost his heart,Christine.In Doctor Strange (2016) he sought answers across the world and in the mystic arts after he lost his abilities and in this universe he does the same for his grief after loosing his love. After becoming The  Sorcerer Supreme he uses the time stone to go back to the exact same night where Christine died in that accident but the accident happened again and again countless times.

A psychic impression of The Ancient One sent through the splinter reality comes to Doctor Strange and tells him that,her death was absolute point in time that's what makes Doctor Strange seek answers in mystic arts.Without her death Doctor Strange would have never have defeated Dormammu,her death was unmovable and unchangable. To gain more power and change what's impossible Doctor Strange tells himself that he needs to gain more knowledge,The Ancient One tries to stop him before he goes to the darkness but she fails.Doctor Strange looks for Lost Library of Cagliostro to gain knowledge that can break absolute point in timex.He gains through absorption of other beings,after gaining the power he becomes more powerful than any other being.

Doctor Strange absorbing Other entity  

When The Ancient One and Doctor Strange fought , The Ancient One Uses her Magic from the dark dimension and splits the timeline. Now for the first time in MCU we saw multi verse through through this episode's two different Doctor Strange.In order to get what he wants Doctor strange have to get merge with himself ,he tries to manipulate him, faughts him and eventually absorbs his old self.

Doctor Strange and his 'Evil Twin'

When Doctor Strange brings Dr. Christine Palmer back from the dead he saw her fading away with the rest of the world,the resulting temperal paradox which was he created was distroying the universe.He takes Christine to the Mirror Dimension hoping nothing will happen to her, The Watcher appeares at that moment Strange begs to him to help saving the universe but The watcher leaves telling him that there's nothing they can do.

Only meddling with time causes more distraction,Now the whole world gets distroyed leaving Dr.Strange alone in the mirror dimension.

"One life , one choice,one moment can destroy the entire universe".

A superhero will kill you to save the world but a supervillain will kill the whole world to save you.