* Which character you're playing as: Sonic takes fewer hits than Tails or Knuckles.
* Which weapons you use: Using the Spin Dash or Super Peel Out will deal more damage than a standard jump attack.
* The Robot's current health: As the Robot takes damage, it becomes easier to destroy.
Instead of a fixed number of hits, think of it as a gradual process of chipping away at its health. The Death Egg Robot has a large amount of health, so you'll need to be persistent and use your best attacks to take it down.