Exava, Rakdos Blood Witch

Unleash was the mechanic that asked aggressive black-red decks to trade their defense for tempo: take the +1/+1 counter, swing harder, and accept that the creature can never block while it carries one. Most of the cycle made that a binary choice card by card. This one rewrites the math for the whole board. A 3/3 with first strike and haste for four already lands as a willing attacker, but the third ability turns the counter from a personal upgrade into a team signal: every other creature you control wearing a +1/+1 counter swings the turn it arrives. That folds neatly into the rest of the unleashed crew, and it widens past them, because any counter source (a Steel Overseer activation, a graft donor, a proliferate effect) suddenly hands out haste alongside the buff. The design tension is precise. Unleash punishes you for going wide and aggressive by stripping your blockers, so a board built around it is a board that has committed to racing. She makes that commitment pay off faster, converting the very counters that took away your defense into the speed you need to win before defense matters. First strike on her own body keeps her relevant in the combat she encourages, and haste means she starts applying that pressure the moment she resolves. The drawback and the payoff live on the same counter, which is the cleanest expression of what unleash was trying to say.