Crusader Kings III

Easy achievement. For a bloody wedding, you need the accomplished forger perk in the diplomacy tree, or for the murder feast, you need the forever infamous perk in the intrigue tree (I did the feast). Start a custom character (make sure you have achievements activated). I used the Count of Gottingen with a 1066 start. You will have sufficient money for either activity. Set your education at Grey Eminence (for the wedding) or Elusive Shadow (for the feast), and make your age 40 or older, which will give you enough points to get the relevant perk. Stick the rest of your points somewhere (intrigue seems appropriate). Start the game, arrange either a grand wedding or a feast, and choose the relevant bloody/murder option and your target. Go through with the activity choosing options that increase your success, and enjoy the resulting bloodshed. Achievement should unlock when you complete the event.