I would like to know if between 450 - 1500 there was ever a king or maybe a count or duke to abandon "feudalism" and create a centralized state or something like that? Did they maybe even create something like a party or an organisation to further their agenda? But the focus has to be on abandoning the "family dynamic" and vassaldom.
Matthias Corvinus of Hungary did a good deal of this. While he did not "abandon" feudalism, he greatly reduced the power of the nobility, created a standing professional army (the awesomely named "Black Army"), built a meritocratic bureaucracy, and was the first ruler outside of Italy to firmly embrace the teachings of the Renaissance, spending a great deal on patronizing the arts and sciences.
Unfortunately, Corvinus' achievements barely outlived him. Despite the power of his realm under his reign, Hungary was still sandwiched between the aggressive Ottoman Empire, and the recently elected rulers of the Holy Roman Empire...the Habsburgs (who shared the title of King of Hungary with Corvinus). The situation was worsened by an unclear succession, with the nobility quickly embracing the weakest option (a frequent occurrence in Hungarian history) who then undid Corvinus' innovations, leading to the collapse of the Black Army (which he could not pay without Corvinus' unprecedented tax measures).
Only 36 years after his death, Hungary would be conquered (or partitioned if you want to nitpick) by the Ottomans, who would rule the country for 150 years, and an independent Hungary would not be seen again until after WW1 (again, we can nitpick here and talk about the dual monarchy, but that wasn't quite the same thing).
This may fall under what you are talking about, but after the end of the Jagiellonian Dynasty in Poland in 1572, an elective monarchy was formed. Monarch's were nominally chosen either from foreign royal families or other nobles by a majority of the Sejm, which effectively was the Polish parliament composed of every noble in the state.
It is just outside the back end of your time period, but may still be of interest. In 1564, a king abdicated his throne, spitting accusations of embezzlement and corruption. His court failed miserably to actually rule in his absence, and begged for his return, which he agreed to on the condition that he should be made an absolute leader. This same leader declared oprichnina, a 'setting apart,' where he declared a significant portion of his holdings under his absolute rule, and appointed a secret police. This group rampaged amongst the aristocrats in the oprichnina, and eventually were given land grants, replacing the aristocrats they destroyed, and were by accounts worse landlords than the last.
In case you haven't guessed, the land was Russia, and the ruler was Ivan Grozny, who you would generally call "Ivan the Terrible."
The oprichniki would eventually sack the city of Novgorod and later participate in the Russo-Crimean War, where they did not account themselves well. The oprichnina did not survive Ivan Grozny.
The aristocracy of Russia, the boyars, would not regain their prominence until perhaps the reign of Catherine, or arguably into the Romanov era. Some histories blame the oprichnina for the long and unhappy interregnum after Ivan IV Grozny, and various other longstanding problems in Russian history, but there's more to it than that.
However, the oprichnina is exactly what you're looking for. Ivan used extreme violence to replace the old aristocracy with one much more beholden to the tsar. Russia's legendary and long-standing authoritarianism may not begin with, but certainly is indebted to, Ivan IV.