GoT's Most Brutal Tradition Alive and Well in House of the Dragon
There are so many of those, though.
Upon seeing the "Game of Thrones ' Most Brutal Tradition" words, most readers probably start wracking their minds and guessing, what tradition we're talking about. And there are good reason for that, given GoT's nature. So, let's just say right away, that by the "Most Brutal Tradition" we mean GoT's habit to turn weddings from something which is supposed to be joyful into tragic and gruesome events.
The infamous Red Wedding in Season 3 is widely considered the most agonizing part of the show (and the books it was based on), but to that we should add King Joffrey's wedding in Season 4, which ended with the groom fatally poisoned (and was nicknamed the "Purple Wedding"), and wedding of Sansa Stark and Ramsay Bolton, which involved no deaths, but still was as much or more horrific thanks to the groom's sadistic nature.
While Alicent and King Viserys have married in the time skip between Episodes 2 and 3, with their wedding probably being as happy as possible, given their severe age difference, the wedding of Laenor Velarion and Rhaenyra Targaryen in Episode 5 is the first marriage ceremony actually shown in the series. And it sure picks up where GoT left off. The wedding feast, intended to celebrate a union between the two old Valyrian houses, starts peacefully enough, but that does not last. Before its end we see a blunt political challenge, an open accusation of murder, an attempt to disrupt the marriage at the last moment, a man getting brutally beaten to death, and the nervous strain on the King resulting in a demonstration of his failing health before the highest nobles of the realm.
Now, to be sure, there are reasons and excuses why marriage ceremonies can be so dangerous and dramatic in Westeros. With so many nobles, including those from opposed Houses and parties, present in one place, tensions are bound to run high. A peaceful ceremony meant to celebrate formation of a new political union is bound to rub people opposed to that union wrong. An arranged marriage might easily deny the people getting married their passions. Indeed, both statements are true regarding the marriage of Alicent and Viserys.
But the same was true for royal marriages in real life, and they did not end up as unmitigated disasters quite so often. Ultimately, George Martin and the showrunners, adapting his works, simply like their drama too much to waste important social events on something as trifling as joy and happiness.