big, great, silly, stupid
You're an even bigger fool than I thought.

absolute, complete, total, utter
poor (= unfortunate)
old (= used to show sympathy, affection or a lack of respect)
The poor old fool was imprisoned on my account.

young
little
You silly little fool!

feel (esp. BrE), feel like
I felt such a fool when I realized what I'd done. (BrE)
I felt like a fool when I realized what I'd done.

look (esp. BrE), look like
They had left me looking like a fool.

act like, behave like
Stop behaving like a fool!

suffer
She doesn't suffer fools gladly.

call sb
take sb for
He had taken me for a complete fool.

like a fool
Like a fool, I told her everything.

fool of a sth
That fool of a doctor has prescribed me the wrong medicine!

act the fool, play the fool
Stop acting the fool and be serious!
Being an actor doesn't just mean playing the fool.

be no fool, be nobody's fool (= be too clever to be deceived by sb/sth)
She's nobody's fool. She had the car checked by a mechanic before buying it.

make a fool of sb/yourself, make a fool out of sb
She was angry at having been made a fool of.

more fool (sb) (BrE)
I thought it was safe to leave my suitcase there. More fool me (= I was stupid to think so).

completely
easily
She's not easily fooled.

cannot
try to

into
He fooled them into thinking he was a detective.

with
You can't fool me with all that nonsense!

have sb fooled
She had me completely fooled for a moment.