The best way to learn proper English is to read news report, and watch news on TV. Watching TV shows is a great way to learn casual English, slang words, understand culture reference and humor. If you have already watched these shows then you may recall the words used in the following dialogs.

Aw! "The CRUELty. Shae is so CRUEL to me."
Game of Thrones Season 3, Episode 2

The gods were CRUEL
when they saw fit to test my vows.
Game of Thrones Season 1, Episode 9

I'll never be CRUEL to you again.
Game of Thrones Season 1, Episode 6

Is the autumn CRUEL
for letting the flowers die...
The Big Bang Theory Season 4, Episode 18

This is the most CRUEL thing we've done to
Sheldon since we left that fake message...
The Big Bang Theory Season 4, Episode 21