Suicide Black, sometimes called Sui or Sui Black, is an archetype of deck that shares similarities with Sligh or other aggressive Red decks. Unlike Red variants, the primary, and usually only color, in the deck is, appropriately, Black. Decks of the Suicide Black flavor usually use cheap, aggressive black creatures such as Phyrexian Negator, which usually comes with a significant drawback to balance the card. Suicide Black attempts to end the game before these drawbacks would have any significant effect on the game.
Suicide Black decks were more popular when Black still retained short-term mana-boosting cards such as Dark Ritual, which have since been moved into Red's slice of the Color pie and/or significantly weakened. Suicide Black decks would also usually employ a significant amount of Discard, e.g. Hymn to Tourach, as well as removal spells to keep the opponent from interfering with their game plan.