SSH connection hangs out at SSH2_MSG_SERVICE_ACCEPT recieved
From the log trace and from your screenshot one can see that ssh-agent is not running.  That is what is causing your ssh session to hang and not respond.

There might be multiple reasons for your ssh-agent not running, including misconfiguration or conflict between different versions of ssh binaries installed (Apple original one, macports or brew installed).  The best and easier, unless you're sure what you're doing and you have a reason to do it, is to stick with Apple's original.

Try to revert to a backup installation or re-install OSX properly.

This other question on ServerFault (and my answer) may help you further.