Normal keys are forwarded over the
ssh session, so none of those will work. Instead, use the escape sequences. To kill the current session hit subsequently Enter ↵, ~, ..
More of these escape sequences can be listed with Enter ↵, ~, ?:
Supported escape sequences: ~. - terminate session ~B - send a BREAK to the remote system ~R - Request rekey (SSH protocol 2 only) ~# - list forwarded connections ~? - this message ~~ - send the escape character by typing it twice (Note that escapes are only recognized immediately after newline.)