Synonyms of unapproachable in English:

inaccessible, out of reach, beyond reach, unreachable, remote, out of the way, isolated, far-flung, off the map, in the middle of nowhere, in the hinterlands

informal off the beaten track, in the back of beyond, in the sticks, unget-at-able

North American informal jerkwater, in the tall timbers

NZ Australian informal Barcoo, beyond the black stump

aloof, distant, remote, detached, reserved, withdrawn, uncommunicative, guarded, undemonstrative, unresponsive, unforthcoming, unfriendly, unsympathetic, unsociable, cool, cold, icy, chilly, frosty, frigid, stiff, formal, dispassionate

informal stand-offish, offish, off