Valley Dasher

The drawback is the whole pitch: two mana buys a 2/2 with haste, but the moment it can swing, it must. That compulsory attack clause is the oldest aggro-design lever there is, the same tax that priced Juggernaut and the various berserkers before it: you get a body and a speed that overshoot the rate, and you pay by surrendering the choice to hold back. Haste makes the constraint bite immediately, since the creature is already legal to attack the turn it lands, with no summoning-sick turn to let you blink and reassess. It cannot block effectively (it would rather be elsewhere), it walks into ambushes a smarter creature would respect, and it cannot sit home to defend a planeswalker or a life total. What it can do is contribute damage on a clock that started one turn earlier than the opponent expected. This is a creature built for a deck that has already decided it is the aggressor and never intends to change its mind, where the "must attack" line is not a cost at all because attacking was the plan regardless. Outside that posture the clause is a liability that turns a fragile two-drop into a recurring tactical mistake the controller is forced to make. The card knows exactly which game it wants to play and refuses to play any other.