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.

Delos:
Most POTENT thing
these cretins will give me
Westworld Season 2, Episode 4

Most POTENT thing
these cretins'll give me
Westworld Season 2, Episode 4

The narcotic effect
is far more POTENT.
Breaking Bad Season 4, Episode 8

You're a POTENT man.
Game of Thrones Season 6, Episode 8

♪ This POTENT drug's runnin'
Through the city ♪
Breaking Bad Season 2, Episode 7