completely; absolutely; totally
「万」 has another reading with different meanings.
10,000; ten thousand
万が一に備えておこう。
Let's prepare just in case.
万全の準備で試合に臨んだ。
I went into the match fully prepared.
万事うまくいくように祈っているから安心して。
I'm praying everything goes well, so don't worry.