Android Question Rooted Devices, kill another app!

Hi, my client wants me to kill another app, his devices are all rooted.

I have tried the os library, it seems to kill the app then it restarts!

So is it possible 100%?

i presume i would need to get root access with my app first but cant find any information on this.

and in theory the OS.killprocess would work?

Is that right?

Thanks

Aidy