Doomsday + Commander's Sphere + Bolas's Citadel + Aetherflux Reservoir + Black Sun's Zenith

Doomsday

Commander's Sphere

Bolas's Citadel

Aetherflux Reservoir

Black Sun's Zenith

How it works

1. Cast Doomsday by paying , searching your library and graveyard for Bolas's Citadel, Aetherflux Reservoir, two other cards with mana value 2 or less, and Black Sun's Zenith, and then placing the remaining cards on top of your library in the order previously listed and losing half your life, rounded up.
2. Activate Commander's Sphere's first ability by tapping it, adding one mana of any color.
3. Activate Commander's Sphere's second ability by sacrificing it, causing you to draw a card.
4. Cast Bolas's Citadel by paying 3.
5. Cast Aetherflux Reservoir from your library by paying 4 life.
6. Cast two other cards with mana value 2 or less.
7. Aetherflux Reservoir triggers, gaining you 1 life for each spell you have cast this turn.
8. Cast Black Sun's Zenith by paying 2 life and shuffling it into the library.
9. Aetherflux Reservoir triggers, gaining you 1 life for each spell you have cast this turn.
10. Repeat until your life total is 53 or greater.
11. Activate Aetherflux Reservoir by paying 50 life, dealing 50 damages to any target.
12. Repeat from step 8.