Android Malware topic

I have an Android device that has been infected with some sort of RAT or trojan horse (I suspect AndroRAT or Adwind, but I'm not too sure). I have tried resetting it back to factory settings, but the malware is still there. Will re-flashing the stock firmware get rid of it? Even if it is embedded deep into the system or into the kernel? If this is the case, how can I get rid of it? There seems to be no powerful Android Antiviruses at the moment. I want to make sure it is 100% completely removed. All input will be greatly appreciated!