If you don't want to waste time using other balls, yes, u should. But it is possible to nab him with another ball. Lueroi, a good YouTube video maker, caught Mewtwo with a GREAT BAll. He used his master ball on something else. If you don't want to waste your MAster ball, don't.
You probally want to use it on mewtwo because it is level 70
Save your MasterBall for the Ledgendary dog (Suicune, Entei or Raikou). Don't use it on Mewtwo because it is really easy to catch him with just ultra balls. Just make sure you save before you fight Mewtwo :)
Mewtwo I guess????
no- at least not to start the battle you should try to catch it with something else you should use master ball as a last resort
Your strongest pokemon and one the that has something to put it to sleep that's how I caught the three legendary birds and mewtwo is next. So long as you remember not to use you're masterball, it should be fine. save right before you attack though, or you may accidentally kill it.
I think you should use ur masterball on entei raikou or sourcune and maybey mew not mewtwo
masterball
It isn't meant for any one pokemon. Most people use it on Mewtwo, which you probably should use it on. You can catch the legendary birds and Mewtwo without a Masterball but it can take a long time.
masterball
you can use it when ever you want but i recomend using it on mewtwo
With a Masterball
You probally want to use it on mewtwo because it is level 70
Use you masterball on suicune because its impossible to catch it without a masterball it would just flee i cuaght mewtwo with a great ball but make sure you have lots of them.
MasterBall
the masterball is for any Pokemon you want, it can catch them without fail ( it will ALLWAYS work ) . you are supposed to use it for mewtwo though. :P
Save your MasterBall for the Ledgendary dog (Suicune, Entei or Raikou). Don't use it on Mewtwo because it is really easy to catch him with just ultra balls. Just make sure you save before you fight Mewtwo :)
you have to save your masterball no matter what and use it on mewtwo in order to catch it faster. otherwise, you are going to spend hours trying to catch it without any luck.