остановись

one more very common word for saying 'stop' that no one mentioned: хвАтит!

good universal word - хорОш!

If you wanna say in russian "stop doing something" you should say simply one word: "перестАнь" (А - is the stress here). It's VERY common and popular expression in Russian. Example: when someone is disturbing you with his comlaints, you may say: Перестань! (Stop complaining!) One this word includes all meaning.

Wenn you use "stop + the infinitive", for example: He stopped to buy a newspaper" it means he stopped his movement to buy a newspaper. In Russian "Он остановился, чтобы купить газету" "Stop + the gerund" means "give up doing something". He stopped buying newspapers = Он перестал покупать газеты.