Hello, Since you have not stated the kind of device you are using, I will give you a general solution on how to remove hangouts both in chrome browser and PC.
Removing from Chrome browser.
We will start by removing the hangouts extension which can be installed as a chrome extension. To do this open chrome browser->navigate to the top right corner and click on the three dots (Customize and control google Chrome)-> click on more tools->Extensions->Click on Disable->Then Remove
Removing Hangouts from Computer.
This will ensure that google hangouts is removed completely from your system. To do so, open your browser and Login to your Gmail account-> On the left panel under hangouts in your account, click on the arrow down just after your name->Scroll down to Sign out of Hangouts-> Go to settings on the top right corner and click on see all settings-> Select Chat and meet tab-> Finally click on hangouts off-> Finally Save changes to remove hangouts from from your computer.