Chandra, Awakened Inferno
This spell can’t be countered.
+2: Each opponent gets an emblem with “At the beginning of your upkeep, this emblem deals 1 damage to you.”
-3: Chandra, Awakened Inferno deals 3 damage to each non-elemental creature.
-X: Chandra, Awakened Inferno deals X damage to target creature or planeswalker. If a permanent dealt damage this way would die this turn, exile it instead.
At 6 mana, it's fine. In most red decks, if I even have six mana, I'm dead.
In short, it is literally everything my Jeskai control deck would have wanted (particularly when I can play Brought Back on her after my opponent kills her on their turn and clear their board or add an emblem).