[ConcernedCitizen]

I have a huge collection of RATs, but i am looking for the most stealthy one. And RemCos is the most recommended for all the options it has. If you can suggest another one that, i prefer that the client that you send to the target can bypass most of antivirus. Many living organisms recommended RemCos.

Any functional remote administration tools will work for you. Your problem is crypting. There are open source crypters available, you just have to look. A good one is msfvenom. It's part of the Metasploit Framework. If you can't do something as simple as crypt I have bad news, no offense.

i don't know how to crypt, i will make my research and see what i can do. If you can show me or help me, it would make my day. And also, is it because of the crypting problem that i can't have the pro version of RemCos ?

Crypting obfuscates the code or stub to make it pass antivirus. You can read about it here and I will not provide links to known (illegal) crypters. You can create your own to bypass antivirus using open source tools.