see (someone/something) for what (they) (really) are

to start to understand the truth about someone or something, especially when the truth is bad.

She suddenly saw him for what he was - a cold-hearted, calculating killer.

• know a thing or two
• know backwards
• know backwards and forwards
• know beans about
• know beans about something
• know best
• know better
• know better than to
• know better than to do something
• know by heart
• know by sight
• know different
• know from Adam
• know if are coming or going
• know if you are coming or going
• know inside out
• know like the back of hand
• know like the back of your hand
• know no bounds
• know of
• know off by heart
• know of someone
• know of something
• know onions
• know place