Before starting, you have to make sure you have access to the victim's smartphone because you will need to hack the victim's phone before the whatsapp.
Follow the steps below carefully .
1. Go to the victim's cells phone and install an application called "AirDroid: File & Notifications"
2. Launch the app, sign up with an email and password, then go-to http://web.airdroid.com/ and you will enter the same email and password that you put in the app.
3. When the above steps is done successfully ,then the phone has been hacked because any message or notification your victim get, you will also get it on the site you registered.
4. Now let's get down to business, you need to download a 3rd party whatsapp on your phone like Gbwhatsapp or OGwhatsapp or better still use any stable app cloner to create another whatsapp on your phone.
5. With the 3rd party whatsapp, log in on whatsapp with the victim's number.
6. The whatsapp verification code will be sent to the victim's number. All you need to do is to get the code from the site in step 2 and input it in the whatsapp.
7. Whatsapp Hacked! Now you can see everything on the victim's whatsapp from your phone.
Note: for this hack to be very effective, make sure the victim's smartphone is "background data enabled"