Yamete vs Yamero

[Sai]

I hear these all the time in anime and i think they both mean stop, but why is there two different ways of using the same verb (im assuming they originate from the same verb yameru), anyways i'd like some answers if you have any

[Hi-Deki]

yamete - give it up / don't do it (command form / as it's just being said)
yamero - (informal / forceful way of saying it)