This is also a boss fight. During the bus drive, you will need to choose the lane that is not marked with danger incoming, and after dodging several hazards, the boss will appear behind you.
Dodge the bosses attacks by switching lanes and then throw a bomb at them when hes finished attacking with
. Repeat that until the boss becomes large and stops behind you.
Dodge the boss's attacks and throw a bomb once you see an eye ball on each limb. Taking out both arms then the head unlocking the achievement in the cutscene.