Unlike Propaganda, which is mainly about ideas being "forced" into another person, Tyranny is a character "vice of excess" that is more vicious and destructive in other ways than just in ideas - financial, moral, social, even physicality may be a portion of Tyranny. A vice stemming from what would otherwise be a character virtue of Authority. It is too much dispensing of authority over achieving a goal, and like any feature of psychology, can have a range - from mere "bossy" behavior, all the way to outright abuse. In Tyranny, the partner issuing it is likely trying to control or change the other partner in some way, to fit their own life's goals - their "mission in life" or "purpose in life."
However, they may also be doing it without any goal at all, simply to dispense with their own anger or rage, and finding the other partner an acceptible (and accepting) recipient. You may notice right in that statement that the immature Ego Defense, called, "Displacement" would be used in order to execute Tyranny. (Learning about the Ego Defenses, you will find them to be a handy, objective measure of a personal character maturity level.)
It is pathologically narcissistic to be tyrannical of course, given that it is pretty much the definition of destructiveness, and "win/lose" behavior - confrontational with hostility for no good purpose, manipulative perhaps, or just outright abusive, Tyranny may come out late in codependence, when one or the other partner starts to dominate all the psychological resources of the couple, selfishly.
The other vice of Authority as a virtue is called, "Abdication," where a person "throws up their hands" in terms of Authority.
Someone who issues "tyranny," is by definition, controlling in nature, of poor boundaries, narcissistic, and disregarding of the sacrosanct nature of your "purpose" or "mission" in life. Your life's goals and dreams are the most precious things you have, more even than the romance itself. Tyranny, or abuse, directed counter to the goals and dreams of a mate shows poor boundaries and a lack of respect for the very life of the other person, beyond even their ideas or emotions. It is their spirit itself - their masculinity or femininity - that is at risk of being hijacked or depleted, and needs their own recapturing of equal Authority in the relationship as its virtuous cure.
As a vice which makes partnership within relationships fail to get to goals, and intellectually unattractive, consider this vice to be negative in many ways, including in sexual attraction, since it actually depletes the reserves of one's own, or the other partner's masculinity or femininity, making them less attractive and feeling less attracted back to you.