Let's stick with the fundamentals first. The "paranoid reactivity" traces back to the six's fundamental distortion that the world is a dangerous place....hence the core desire for the six is to avoid being harmed (ex. duped, conned, controlled, attacked, pushed around, picked on). Thus, the main interest of the six is self-protection and the main avoidance a sense of inferiority/victimization. With eight, the core avoidance is whatever you would call the state of not exercising power (ex. weakness, passivity, dependence, tender-mindedness).
Two underlying behavioral dynamics to take note of with type six include the exculpation of guilt onto others and the projection of hostility. The phobic solution is as exaggerated in its submission towards the object of perceived hostility as the counterphobic solution is exaggerated in its againstness towards the object of perceived hostility. Most sixes swing between a phobic - counterphobic style, but some are predominately one or the other. In the predominately counterphobic six, the key characteristics are bluffing and pugnaciousness - which, essentially, is a prolonged fight response to the perceived fear object. This exaggerated againstness on the perceived object of fear captures the essence of the counterphobic six. See Sheriff John Wydell in the Devil's Rejects for a great example of a counterphobic six. Captain Ahab is another example of the counterphobic six.
In contrast to eights, sixes typically have a life pattern of falling behind the eight-ball due to interpersonal conflicts. They have a fundamentally adversarial nature that can manifest, as previously pointed out, through an exaggerated againstness and they can devote their entire lives to taking people down, for better or worse (the vigilante; the adversary, 'diablo')….a good portion of their aggressiveness goes towards ensuring that they are not made to feel inferior. But what happens when there is no fire to put out, when there are no external triggers to react to....the non-provoked state is where its easiest to see differences emerge. more productive sixes are prone to try and get what they want by hinting at what they want and approach business with an aim towards establishing strong alliances. sixes will call upon the authorities when they sense it can give them an advantage in a conflict whereas eights see 'running to the authorities' as weak. If you're talking about say an 8 and a 6 working at a job, the 8 won't have any problem asserting themselves for a raise or promotion; the 6 otoh will have to work themselves up for the event or wait until an external trigger fires them up and contraphobically lay it down, usually going overboard in the process and making a grave mis-calculation. They are sometimes assertive whereas the 8 is assertive 24/7.
In contrast to sixes, eights have an entirely aggressive personality -- somebody with the requisite temperament for outwitting, outmanuevering, and outmuscling others in order to acquire their own spot at the top of the mountain. They typically have a life pattern of empire building from scratch, resource acquisition, and using aggression instrumentally in order to preserve their own dominance/control/order. They are instinctually drawn to environments where boldness and hard-headed realism pays off, they are comfortable giving orders, and don't see a problem with using savage, diabolical methods. [As a point of note, Saddam Hussein, Idi Amin and Al Capone had their own personal torture chambers. Capone was known for spending all night in there.] The thing to look for is that whatever position you find the eight in they will use that position in the most aggressive manner possible but not at the expense of being incompetent at that position or presenting one's self masochistically (if that makes sense)….more often than not eights get their way. Aggression itself is a competency for getting ahead. They overexpress gut energy so express anger easily in the present moment but once it passes there's no trace left behind. In the less healthy levels, the eight is susceptible to engaging in criminal behavior through the use of violence and using intimidation/threats/manipulation of resources to make people do what they want and hold onto/expand their power base.