If you wish to delete any game from your Steam Library, you can follow these steps:
- Start the Steam Client and click on Help at the top of the window and select Steam Support
- Select Games, Software, etc.
- Select the game you wish to delete
- Select I want to permanently remove this game from my account
- Select Ok, remove the listed games from my account permanently
Please keep in mind that if you permanently delete a game from your Steam Library, it will also remove any purchases you have made.
You can also hide a game in your Steam Library:
- In your Steam Library, right-click on the game you wish to hide and select Set Categories
- Check the box Hide this game in my library