He didn't listen to Varys,
who tried to WARN him.
Game of Thrones Season 3, Episode 5
...someone called to WARN him.
Breaking Bad Season 3, Episode 9
You said,
"I did WARN you not to trust me."
Game of Thrones Season 7, Episode 7
Go on, then. Warn me.
Game of Thrones Season 2, Episode 8
Great.
I just have to WARN you,
The Big Bang Theory Season 7, Episode 24