Elektra, Daughter of the Hand

The Sneak keyword is a discount tied to a bluff: it lets a body arrive from your hand in the middle of combat, but only if you first swing with a creature that the opponent chooses not to block, then yank it back. That timing is the whole design. You declare attackers, the defender decides where to spend blocks, and during declare blockers you convert an unblocked attacker into a fresh 3/3 that enters tapped and attacking. The reward for threading that window is a two-for-one: the returned creature is safe in hand, the new one hits, and her enter trigger deletes an opposing creature with power 3 or less. In practice she punishes an opponent who under-commits blockers, and she asks a real question of one who over-commits (every creature held back to block is a creature the defender can't use to stabilize the removal that follows). The power-3-or-less clause is the discipline on the removal: she clears the small and the utility, the mana dorks and the evasive one-drops, but leaves the genuine top end alone, which keeps her honest as a tempo piece rather than an unconditional answer. What makes her more than a combat trick with a body is that she rewards you for building a board of expendable attackers whose job is to bait, not connect, then cashing one of them in at the exact moment blocks are locked.