This can be via being banished, sent to the Inkwell, the deck, or (most importantly) the hand
Ruinous Ultimatum (33/53) Tran Nguyen Kefka is a personal favorite from both Final Fantasy VI and Final Fantasy XIV
In decks with a low mana curve that want to cast a lot of spells, Lightning Bolt is also a signature piece of the strategy
Gishath, Suns Avatar When youre doing dinosaurs, the deck's focus is always going big and fast
When Loyal Warhound enters the battlefield, if an opponent controls more lands than you, search your library for a basic Plains card, put it onto the battlefield tapped, then shuffle
So often I build five colour control decks and realise just as I am putting the finishing touches on it I really struggle to win and need an actual threat