"앞만 보는 불도저" => (literally) A bulldozer(불도저) that only(만) faces(보는) forward (앞) => A bulldozer that only goes forward / A bulldozer that only knows to go forward. It is a phrase describing someone who works toward his goal like a bulldozer never tiring or changing course, overcoming what gets in the way. But from what I've seen, it is more common to say 앞만 보고 가는/전진하는/달리는 불도저.