For when you really want to make sure he's dead (Modern)

How to accomplish a 8-duodecillion damage + combo.

With exactly 21 mana and 0 cards in deck, you first cast overblaze on your first spitemare. Your opponent then starts to tremble in fear as you cast shivan meteor on the aforementioned spitemare, which screams in agony after being dealt 218,103,808 damage. This spitemare then passes on the pain to the second spitemare, dealing 457,396,837,154,816 damage. As your opponents face begins to melt from the fireball which has spontaneously appeared on the table in front of them, the next spitemare disintegrates after taking 479,615,345,916,448,342,016 damage. The final spitemare then spontaneously combusts once it takes 502,913,140,959,685,736,677,769,216 damage. Despite being indestructible, your stuffy doll is somehow removed not only from the game, but from reality itself, once it is dealt 527,342,649,694,943,431,022,628,533,436,416 damage. If your opponent hasn't died yet from the fireball growing on the stack, they take 8,847,341,539,944,400,050,047,739,793,225,973,497,856 damage. This is more than most declared life totals after "infinite" health combos, meaning you most likely win the game.

Unless they have a counterspell, that is.