Missile Tractor is the boss of Level 50 in Bubble Bobble Part 2.
This Miniboss is large, moves with decent speed (but thankfully doesn't seek you) and can shoot three missiles upward that spread out as they fly. You first move should be to wrap around the screen from left to right, float up, past the Hoppits, to the top platform. Star Bubbles appear in this round, and that makes this fight easy. The first star bubble you pop will likely destroy all the Hoppits. Just dodge his attacks (easy, they can't reach you on the top platform) and wait for 'Clear' after you beat the Hoppits. Yes, that's right, you don't have to beat the tractor to win.