hi i know displaying any parts of private key is dangerous ( Especially the first character ! )
is possible Brute-force attack ethereum private key missing a 20 character ?!
Ethereum is off-topic, but this applies to Bitcoin as well, so why not answer it?
No, it's highly unlikely that a brute-force attack against 20 missing characters of a private key is to succeed.
For a
very very rough estimate, you may consider the performance of the software of vanitygen, which basically is highly optimized brute-force-software for keys.
Anything longer than 10 to 12 characters seems to be bordering on impossible, given standard hardware.