Solus

Solus can be seen as the main antogonist throughout BREAKDOWN, although he states that he is "just Nexus' avatar." He is incredibly powerful, more-so than Derrick, and has never been defeated in combat. His name, Solus, is latin for alone. This seems to suggest that he is lonely, inhuman, and figuratively dead inside. His name is also likely a play on the word soulless (without a soul). The first time Derrick encounters Solus, Alex tells him to hide. They witness Solus choke a researcher to death with one hand and toss him aside. After Solus leaves, Alex informs Derrick [something, likely important, can't recall].

Derrick later encounters Solus in a large office-space. After a brief fight (during which it is clear that Derrick is severely outclassed), Derrick is thrown against a window and dropped (at first, appearing to fall from the building), but, much to his surprise, Solus allows him to live. It can be inferred that Solus has an interest for Derrick and wishes to have a more challenging fight at a later time.

At yet another point, Derrick flees from Solus while simultaneously avoiding Claymores. Reinforcing the fact that he is more or less "invincible," Solus simply walks through these explosives unscathed, setting Derrick's nerves on edge. [somehow Derrick escapes...] Solus later takes Alex captive and uses her as bait to draw Derrick out. When Derrick frees her, Solus appears, informing Derrick to "Leave the female... baggage" and initiates a fight. During this confrontation, Derrick manages to knock Solus down, at first thinking him defeated. In response to this, Solus (much to his own surprise) remarks "Not finished yet" as he stands up. After this, however, Solus near-effortlessly defeats Derrick. Afterwards, Derrick hears a radio call informing him of what will happen soon from outside Site Zero whilst watching a battered Alex's futile attempt to fight Solus off, but fails, with Solus easily beating her back down to Derrick's side, Solus watches Alex give her final words to Derrick, dying in his arms shortly after shedding a single tear. Unamused, he remarks "Impossible. Game: Over,", and then the missile fired as part of Operation No Return collides with his shield (ironically inscribed with the words: "Game Over"). The resulting explosion causes a temporal rift which sends Derrick fifteen years into the future. After returning to the past, Derrick again comes to the pivotal battle with Solus. Now armed with the Ultra-Accelerator, Derrick is able to fight with Solus as a near-equal (though it is likely that Solus may still be more powerful than him). As Solus begins to be overwhelmed by Derrick, his attitude begins to deviate. His comments become more stressed and he begins to sound more human. His prior arrogance fades as he struggles for dominance. When he is finally defeated by Derrick, the synthesized inflection in his voice disappears as he states in what appears to be a saddened tone, "Derrick... Derrick... Remember... I... am just... Nexus'... Avatar..." After which, his head falls back and his body fades away. Many of Solus' attacks mirror those of Derrick's, albeit in a more powerful form. Additionally, Solus' physical appearance is very similar to Derrick's, being of the same height, build, and facial structure. It is quite possible that Solus is actually Derrick from an alternate time-line. [several of Solus' statements bear further examination]

His final words claim him to simply be an "avatar" for Nexus. This would indicate that he did not choose to become Solus, and he was perhaps forced to do so. It's hypothesized that Derrick very well may have become Solus had he not been able to overcome the mental conditioning imposed upon him by Nexus.