Extrinsic, extraneous, foreign, alien are comparable when they mean external to something or someone or to the true nature or original character of such thing or person.
Extrinsic applies to something which is distinctly outside the thing in question or is derived from something apart from it; thus, a ring may have extrinsic value because of sentimental or historical associations; such extrinsic influences as chance or the assistance of friends may help a man to succeed.
Extraneous, though often used interchangeably with extrinsic, applies more specifically to something which is introduced from outside and may or may not be capable of becoming an integral part of the thing.
Foreign applies to something which is so different from the thing under consideration that it is either inadmissible because repellent or, if admitted, incapable of becoming identified with it, assimilated by it, or related to it.
Alien applies to something which is so foreign that it can never be made an inherent or an integral part of a thing. The word often suggests repugnance or at least incompatibility or irreconcilableness.