Voldaren Duelist

The enters-the-battlefield clause is doing all the work here: a hasty 3/2 that arrives swinging is fine but forgettable, and stapling "target creature can't block" to its arrival turns the body into a combat trick you can leave on the board. The Vampire shows up, pins the one blocker between an aggressive board and lethal, and adds three power of its own to the swing. Because the rider triggers on entry rather than on attack, timing is the whole tension: cast it on a developing turn and the can't-block has already worn off by the time you need it, so the card rewards holding it until the attack it can actually break open. Haste closes that loop, letting the creature clear a lane and run through it the same turn instead of telegraphing the plan a turn early. What keeps it honest is how narrow the effect is: it neutralizes one creature for one turn, does not kill, does not tap, and a fresh chump still trades or a second blocker still gums up the assault. This is a red creature that pays for the permanence of a 3/2 by giving up the raw efficiency of a dedicated removal spell. Where it earns its slot is on a wide, racing board, when the defender has exactly one meaningful wall and pulling that wall aside is the difference between a stalled turn and a lethal one.