Open Steam
Go to your Library
Right-click the game you want to remove
Select Manage
Click Uninstall to remove the game files from your computer
To hide the game from your library, right-click the game
Select Manage
Click Hide this game
To permanently remove the game from your account, open Steam Support
Select the game
Choose I want to permanently remove this game from my account
Confirm the removal
To remove a non-Steam shortcut, right-click it in the Library
Select Remove from Favorites or Delete shortcut if available