User blog comment:Diyartifact/Shepard's adversaries/@comment-1895174-20120408234519/@comment-2079715-20120410010911

I don't think that we can put villains in brackets so easily. Saren was Indoctrinated by Sovereign, but still was able to think by himself in given situations. Sovereign and Saren and the Geth were separate beings. While Collectors are just Prothean Husks. Mordin says it himself. Collector's anatomy forbids Collectors to have any thought of their own. They are empty shells, waiting to be possessed by Harbinger, unlike Saren or the geth. They have no brain functions like normal organics or even synthetics like the geth. They don't feel anything, "they don't have art" - Mordin, again.

So i say it's safe to presume that EVERY fight against Collectors in ME2 was the fight against the Harbinger himself.