Inferno Elemental

The flavor of a fire elemental that scorches whatever it touches in combat, rendered as a deterrent priced for the patient: a 4/4 that punishes the engagement before damage is even exchanged. The 3 damage to anything it blocks or is blocked by means small creatures (3 or less toughness) die on contact, dealing nothing back, while the body shrugs off most of what trades in that range. The math only frays at the top: a creature with 4 or more toughness survives the trigger, and a beater big enough to push 4 power through will kill the Elemental in the exchange, so this is a wall against the swarm, not against the genuine threats. The cost is the rest of the story. Six mana for a body that does its best work standing still is slow, the ability fires only in combat (so the turn it resolves it merely sits there waiting to be attacked into), and it never touches the cards the opponent keeps in hand. That places it at the top of a casual creature curve rather than a competitive one: a single hard-to-attack-through blocker with a punitive edge, doing the deterrent work that first strike or deathtouch does elsewhere, just by the more literal route of burning the blocker rather than out-fighting it.