I am looking for an adjective akin to "loyal" and "disloyal" in that it describes someone's exact null association with both words. Someone or something with no allegiances whatsoever, a goes-with-the-highest-bidder kind of person. Someone or something that can be the perfect model companion or machine or tool or concept, and then without warning he/she/it may whimsically and deliberately, yet completely uncomprehendingly, do something utterly devastating or infuriating to you, and have no idea that you may have considered it wrong, or even may have legitimately believed they were going out of their way to act in your favor.
Benevolent, though perhaps unwittingly and unpredictably deleterious.
The words I am looking for are not these: "non-partisan", "ambivalent", "apathetic".