If you're looking for a quick way to die 100 times just to get this done...
On level 2, keep going until you find the part just after the bee hive where there's a platform you need to jump on thats moving up and down. If you walk off the ledge, you'll drop down onto the red spikes below. (see video below)
When you die, you'll quickly respawn back up on the ledge, allowing you to walk to the right to drop to your impending death again.
Continue doing this and you'll easily rack up 100 deaths with little effort.
Note:
I have a standard Xbox One controller. I was able to set the controller next to me on my couch in a way that the couch would hold the joystick in place to keep my character running to the right repeatedly every time he would respawn. Took about 5 minutes for the achievement to pop. Doing it this way you can even walk away for a minute and let the game rack up some deaths.
Have fun dying!
